JUNE 26, 1891.

ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1370.

upon the ground at the place in question were allowed to remain upon the ground, no drop of it passing into the soil or evaporating into the air, the ground would be covered by a layer of water so many inches, say 20in., deep.

snow,

INSULATING SUSPENSION FOR
ARC LAMPS.

water especially, becomes so great that the spring, as it hurries on to form part of some The geological water cannot hold it all in solution, and some of river, deposits by the way quantities of the solid it crystallises out in the solid form. Especially matter that it has worn away and transferred. is this crystallisation and deposition of solid The springs empty into rivers. matter likely to occur in the case of calcium work of rivers will occupy us next. For, as we have noted Two things should be kept in mind when we carbonate in one or other of its forms-chalk, are talking or reading about inches of rainfall. limestone, marble. (1) That rainfall" includes all kinds of water several times, this salt is insoluble in water that falling in any form from air to earth-rain, does not also contain free carbon dioxide. But as a spring goes bubbling along, the carbon hail, hoar-frost, and dew. (2) That an inch in depth of rain means about 100 tons dioxide, that is the chief cause of its bubbles, passes off from it into the air; and this the weight of water fallen upon an acre of ground. The rainfall varies greatly during given periods more, seeing that this carbon dioxide has been of time, and especially with given places. Here dissolved underground and under pressure. we can only note one or two points in connection When the water comes up from subterranean an open soda-water or with local variations. The average annual rain-depths to the surface of the ground, the case is similar to that of champagne bottle. The pressure being removed under which the gas was dissolved and retained, the gas, now escapes.

fall for the whole of the British Isles is about The rain36in. For London it is about 24in. fall in the British Isles is greater in the west than in the east; is greater in the north than in the south. This difference is probably dependent upon, as it is certainly connected with, the more mountainous nature of the west and of the north as compared with the east and with the south. The mountains attract the floating cloud The place in vapours in the form of rain. England where the rainfall is greatest is near Seathwaite in Cumberland: here the yearly average is 165in.

But this 165in. of rainfall, great as it is compared with the 24in. of London, is small compared with the rainfall in tropical regions. In these last 200in. is common enough; but the Khasi Hills, some 100 miles north-east of Calcutta, are the rainiest place in the world : there the yearly rainfall is some 524in. Upon the other hand, there are rainless regions, such as the desert of Sahara.

Of course, rain, when it falls upon the earth, does not lie thereupon in a constantly and It runs off the uniformly increasing layer.

surface unless the surface is level. It evaporates. Above all, it sinks into the ground. Only by the use of a rain-gauge, such as that shown in Fig. 20, can the rainfall be measured. F is a funnel, and V is a vessel, both of metal. Obviously almost the whole of the rain falling upon an area of the ground equal to that of the opening A, can here be collected in V, and is subjected to almost no evaporation.

the

But the ordinary rain not caught by a rainAbove all, gauge runs off, evaporates, sinks. as I wrote above, it sinks into the ground, sometimes to great depths. Always, in making its way through the earth, the rain-water, now gradating towards spring water, carries along suspended and dissolved matters, and greater the depths to which it sinks, and at which it works, the larger the amount of soluble matter it dissolves. For in the first place the greater the depth, the greater the number of rocks, and therefore the greater the quantity of soluble matter with which the water comes into contact.

Sooner or later, the water that has been making its way underground comes to the surface. And then it is spring water, to the consideration of the geological action of which we now pass.

Moreover, at greater depths, and under the greater pressure that occurs at those depths, water can, and does, dissolve proportionately larger amounts of the gases it encounters, and especially of the all-important carbon dioxide.

(b) The Action of Spring-Water. From that which has been said, it is clear that the action of spring-water will be still a continuation of the process of denudation and transference. The spring, in its course, will wear away and dissolve the rock materials of its bed and banks. And it will do this the more For as the volume and effectively in both ways. velocity of spring-water are both greater than those of rain-water, much more rock material will be carried away in suspension by the springs than even by the rain. And, again, the chemical action of spring-water is much greater than that of rain; for it contains much more solid matter in solution, and especially is likely to contain much more free carbon dioxide gas in solution. And this, as we saw in the last chapter, enables water to dissolve calcium carbonate, which is not soluble in water that contains no free carbon dioxide.

THE is the invention of HE insulating suspension, as shown in the Mr. James Raeburn, of Glasgow. It is well structed arc lamps, and to prevent this leakage known that in damp weather there is considerable leakage to the frames of even the best con

From whichever of these two causes it may
be that the free dissolved carbon dioxide escapes,
the result is the same, as far as any calcium
carbonate in solution is concerned. This salt
will be at once thrown down, or precipitated in
A particular case of this deposi-
the solid form.
tion of calcium carbonate and the formation of
calcareous deposits occurs in stalactites and
stalagmites. These occur in caverns in districts
rich in springs.

Spring water, impregnated with calcium

the fissures in its roof.

SECTION ON A B

B

been

the

going to earth, this suspension has
As is self-evident from
constructed.
drawing, the weight of the lamp hanging on the
hook is borne by the balls inside the hollow
casting, the balls being made of a hard, in-
sulating material, such as glass or porcelain ;
thus the part of the suspension which forms the
insulator is protected from rain or snow, giving
a high electrical insulation in all weathers.

carbonate and free carbon dioxide, is flowing
over the roof of a cavern and filtering through
As drop by drop the
water finds its way to the lower inner surface of
the cavern roof and hangs there, its free carbon
dioxide evaporates, and the calcium carbonate is EDGAR AND MILBURN'S IMPROVED
on the margin of the fissure or of the
deposited
hole, and thus the commencement of a stalactite

BATTERY.

of which is the use of aluminium as the positive plate, has been patented by Mr. Edgar, of Canterbury, and Mr. Milburn, of Newcastleon-Tyne, the special object being the production of a portable battery suitable for miners' lamps. A double fluid cell may be constructed by The cells may be either double fluid or single

AN improved voltaic battery, the chief feature

(st, Fig. 21) is formed. This process, repeated
through months and years and centuries, at
many points in the same cavern, results in the
wonderful stalactitic caverns (see Fig. 21) of
limestone districts. oraλaoow (stallasso), I drop.
Generally, immediately underneath a stalactite
is found a smaller rod of calcareous matter, grow-
ing upwards from the cavern floor. This is due fluid.
to some of the drops of spring-water falling from means of an aluminium plate, which dips into a
the roof of the cavern before all their free car-solution of ammonium chloride and hydrochloric
bon dioxide has been given off, and before all acid, with or without the addition of sulphuric
their dissolved calcium carbonate has been de-acid, and a carbon cylinder, which dips into a
posited. Upon the floor of the cavern, the pro- solution of sodium chloride and nitric acid, or into
Hence there bisulphate. The two liquids are separated from
cess interrupted on the roof by the falling of the nitric acid only, or into a solution of potassium
drop is continued and completed.
results an upgrowth of calcareous matter or a each other by a porous partition, as usual, and
Sometimes the other suitable material. A single fluid cell may
stalagmite (sm, Fig. 21) from the cavern floor. the whole is contained in a cell of ebonite or
oralaya (stalagma), a drop.
ages through which this action continues last so contain a carbon electrode and an aluminium
long that stalactites and stalagmites meet, and electrode, which dip into a cell containing
form vertical pillars, reaching from cavern-roof ammonium chloride, hydrochloric acid and water,
the aluminium electrode or plate being prefer-
to cavern-floor.
ably placed in the centre, while two carbon plates
are placed right and left at a suitable distance
from the aluminium plate, and are connected
with each other externally, so as to form on

Whilst the larger part of the geological work Even more frequent and more extensive in its done by rain and by spring-water is denudation and transference, a certain amount of deposition effects than the deposition of solid matter oriof material must also take place. Sometimes, the ginally held in solution by spring-water is the amount of solid matter in solution, in spring-deposition of matter held in solution. Every

pole. The shape of the electrodes or poles, and of the cells, may, of course, be varied to suit various requirements.

The proportions of ingredients used in the two liquids may vary according to requirements; it is preferred to prepare the liquids for the double fluid battery as follows: 6 parts (by weight) of ammonium chloride (NH,Cl) are dissolved in 30 parts of boiling water, the solution is allowed to cool, and 2 parts of hydrochloric acid are added, to obtain the liquid which acts on the aluminium; while nitric acid (HNO,), or a solution of 6 parts of potassium bisulphate in 15 parts of water, is employed for the carbon plate.

For the single-fluid cell, the following proportions have given good results:

The second example is suitable for electric bells or signals, in which case the carbon electrode or pole has preferably the shape of a block, while the aluminium is used in the shape of a rod or roll.

RETOUCHING AND SPOTTING
PHOTOGRAPHS.

AF

dulness. The degrees of hardness may be
obtained in two ways-first, by increasing the
salts of nitre; secondly, by cooking longer. It
is better to obtain the degrees of hardness by
cooking, as much salts of nitre will make the
crayon too brittle. Copal varnish may also be
used to mix the colour when required harder.
Only two colours are necessary in manufacturing
the retouching crayon-viz., brown and black,
nine parts of each, added to the ingredients
before mentioned, leaving out the other colours.
The crayon can be used on the negative film
without the retouching medium, or can be used
on the retouching medium without the negative
varnish. Should the retoucher accidentally
stipple too heavily, the spots can be reduced to
the shade required by the point of a brass pin,
not too sharp, or can be removed by rubbing
with a piece of pointed ink-eraser, or piece of
chamois leather over the finger, without re-
moving the varnish or retouching medium, in the
usual way with methylated spirit.

THE

THE CHEMISTRY OF FRUIT. HE chemist at the Agricultural Experiment Station, Geneva, N.Y., has recently published a paper which may be of special use to those gardeners who have even an elementary acquaintance with chemistry. As most people are aware, fruits of nearly all sorts contain a large percentage of water, and Dr. Van Slyke's FTER printing and toning, photographs are figures may vary from others, for something often found to have white spots, and the depends on the season and the soil. Thus for mediums employed to cover them are often re- strawberries and raspberries he gives 88 per cent. moved in the enamelling and burnishing pro- of water, pears and apples 84-85 per cent., cesses. Mr. Beacham, of Litchfield-street, Soho, plums and peaches 80-81 per cent., cherries 80, W.C., has patented a crayon for spotting and and grapes 78 per cent. Very little albuminoid retouching, which is made as follows: White matters are found in fruits and still less starch, wax, 32 parts; curd, yellow, or Castile soap, but carbohydrates, especially in the form of 27 parts; mutton suet, 4 parts; salts of nitre, sugar and cellulose, have a respectable percentage 1 part, dissolved in eight times its weight of of the fruits mentioned grapes containing the water; pitch, 4 parts; shellac, 6 parts; calcined largest amount of sugar-14 per cent., as comlampblack, 4 parts; dyes or stains in powder-pared with 4 per cent. in plums. The latter brown 7 parts, scarlet 3 parts, blue 3 parts, violet 3 parts. These colours produce a useful photo-shade, but the proportions can be varied according to the shade required; other colours can also be produced if required. As soap contains more or less moisture, according to age, it must be cut into small pieces and dried before ucing. The suet and wax are first melted; the soap, having previously been cut into small pieces, is then added a small piece at a time, allowing each piece to dissolve before another is added. When dissolved, they are allowed to burn until reduced to the same volume as before the soap was added. Care must be taken not to allow them to burn too much or too quickly (it may be necessary to take the vessel off the fire to prevent the contents from boiling over). The flame is then put out. When these three ingredients are dissolved, and the salts of nitre has been mixed with eight times its weight of water and warmed, it is added by small quantities to prevent too much effervescence. The shellac and pitch are added. The requisite colours, in powder dyes or stains and calcined lampblack, are mixed with a stiff varnish, or suchlike suitable substance. It is essential for the whole to be dissolved into one substance, and kept stirring during the whole of the foregoing process with an iron spatula or pallet-knife. When a little cool, it is poured out on a marble slab previously rubbed with soap or suet. When set a little, it is cut into small pieces and remelted (remelting is done to give a finer texture to the ingredients), then moulded into suitable form and pointed, finally finishing off the point by rubbing on paper; fine glass paper or emery cloth may be used. In spotting a photograph according to the invention the point of the crayon may be moistened by dipping it in clean water, and if the spots are very obstinate to cover, acetic acid or carbolic acid must be added to the water, about three parts acid to one part water. The acid must always be added to the water when photographs are to be enamelled, and when the film is thin on the negative in spots; if the photographs are spotted in quick succession after mounting, there will be found sufficient moisture to dispense with the use of water, unless the spots are difficult to cover, when the acid, or acid and water, must be used. If photographs are spotted after burnishing, and show dull spots when spotted, a slight rub with piece of clean rag or chamois leather dipped in French chalk will be sufficient to remove the

a

are, however, comparatively rich in pectin
substances, containing even more than apples.
From the physiological point of view, the
great value of fresh ripe fruit depends on the
free acids and the alkaline salts; the flavour
and aroma on the fatty and ethereal oils, which
are present in very minute quantities. The three
acids present in fruit in the order of their amount
are malic, citric, and tartaric, the first being the
most common, and the last (tartaric) in grapes in
greatest quantity. If the question is regarded
from the food-value point of view, then the
soluble constituents of the dried fruit form the
guide, and it is found that apples contain 88 per
cent., as compared with 81 for grapes, pears
coming next with 73 per cent. Plums follow
with 72 per cent., and in this connection are
better than cherries, which have only 67 per
cent. of soluble constituents after all the water
is removed. Strawberries from the point of view
of food-value are a long way in advance of
raspberries, as they have 67 per cent. of soluble
constituents as compared with 46 for raspberries.
Such figures are not, however, an altogether
trustworthy guide as to the value of fruits for
dietetic purposes, as many of the insoluble sub-
stances perform work in the human economy
which is of considerable value on the hygienic
side of the scale. Ripe fruits of all kinds are
good for man, and some of those which contain
the larger percentages of insoluble matters are
even more beneficial in some cases than those
which contain the larger amounts of the more
agreeably tasting constituents. The character
of fruits is, however, influenced to a consider-
able extent by climate, soil, and cultivation, for,
as is well known, apples and strawberries, for
instance, under the care of the gardener, contain
much larger quantities of sugar and are much
more luscious than the wild varieties.

HE electrostatic commutator here shown is a

with corresponding hollows at their rubbing ends, so that when handle is moved the spring slides on and drops into place easily. The screws C and E are connected permanently together by a wire. A Cor E, are for the test wires. This method of conand B are the quadrant terminals; D, and either necting prevents all possible chance of shortcircuiting a cell under test. By sliding the springs

CARTH

becomes +, and that joined to B is -
on to C and D, the quadrant in connection with A
We may
reverse by sliding the springs to D and E respect-
ively. The electrometer quadrants are connected
together by joining A to C and B to E-in which
position the springs should always be left after a
test. In intermediate positions the quadrants are
completely insulated. When very high insulation
is required, some desiccating arrangement may be
employed. With a slight modification of the
handles, a place might be found for this commu-
tator inside the electromotor case itself, the handles
being entirely outside, below the base.-R. APPLE-
YARD, in Electrical Review.

AN ELECTROSTATIC COMMUTATOR.
Tsimple apparatus, of small capacity and high
insulation, for effecting all the ordinary connecting drop on the floor. I shall endeavour to explain a
operations with electrometers. It consists of five simple device which is not patented, and which any
insulating rods, three of which, C, D, E, are fixed; pattern-maker can make for himself with perhaps
A and B are fitted into brass sockets in the base a little aid from some good friend in the machine-
board with spring washers, so as to be capable of shop. This tool not only holds the pattern securely
the top of each fixed rod is a binding screw, tipped instantly when the operation is completed, without
turning about a vertical axis by handles, H. At while being varnished, but also releases the work
with platinum, and having a slightly convex sur-touching it at all with the hands.
A glance at the
face of contact. The rods A B carry contact springs cut will explain the modus operandi. First turn

JUNE 26, 1891.

ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1370.

FIG. 1.-Dabaecker's Baroscopic Thermometer.

the handle, as shown at A, about 3in. in length, and having a very thick ferrule on the end. (A ring cut from the end of a piece of gas-pipe makes an excellent ferrule). Next bore a small hole about in. diameter through its entire length, having the upper end counter-bored in. in diameter and about in. deep. Now on the end of the ferrule drill three small holes equidistant from each other, and insert some steel-wire prongs.

For the plunger to release the work I used a little brass rod having an acorn-shaped tip, such as ladies use for banner-rods and small curtains. This form of tip is excellent, for it will not scratch the work. Cut a thread on the top end of the plungerrod, and screw it into the cap, as shown at B. Have the rod long enough, so that the spiral spring will keep the cap pressed back in. from the main body of the handle. It is a good plan to turn a little groove on the under-side of the cap just the diameter of the spring, so as to hold it in position. The prongs should be about in. longer than the plunger-tip, and filed back for in. or more to sharp, flat points. (I use the word flat in the sense of thin-edged). This form is much better than round points, for the marks left will be scarcely perceptible. To use this tool to the best advantage, hold it in the left hand and strike the work firmly and squarely with the three prongs, and after the pattern is varnished simply press the cap B with the thumb; this will cause the plunger to press the pattern in a point exactly equidistant between the three points, and release it at one without injury. This tool is something I had never seen, but had felt the need of, and so I made one for myself, and it works perfectly. RICHARDSON, in American Machinist.

FIG. 2.-Diagram of Baroscopic Thermometer.

the elevation of the temperature, the second lever
arm will increase in weight to the detriment of the
first. It will therefore descend, and we shall here
have a utilisable force. If care be taken to select
for an expansible body a material not subject to
molecular variations of structure, it is clear that to
a same elevation of temperature there will always
motive force.
correspond a like expansion, and therefore a same

The body employed is mercury, the fluidity of
which perfectly adapts it to the construction of the
apparatus, and the uniformity of expansion of
which secures a perfectly regular operation. More-
over, the great density of this metal gives a great
increase of force for a slight increase of tempera-
ture.

In principle, the baroscopic thermometer devised by Mr. Debaecker is therefore an ordinary thermometer held in equilibrium by means of a horizontal axis passing through its centre of gravity. If the temperature rises, the mercury will expand in the thermometric tube, which will become more weighty and will incline. In case the temperature falls, a contrary effect will follow, and the tube will rise, thus producing an alternating motion capable of being utilised.

The principle upon which the baroscopic thermometer is based being true, it might be constructed of as small dimensions as possible; but what is correct in theory ceases to be so in practice when it is necessary to dispose of an appreciable force in order to render the apparatus sufficiently sensitive, and to compensate for the work absorbed by the movement of the parts.

of the apparatus from the centre of gravity of the reservoir and from the centre of gravity of the small tube and its spherical volution constituting the long arm.

If we deduct from the reservoir a weight, p, the effect produced is the same as if there had been added to the long arm a weight, ?. On the other

hand, if we now add to this arm this same weight p, it will act with a force equal to its own value, and the total effect produced to influence the tube will be equal to

p +

p

.(1)

d, ៤ being the quantity of expanded mercury necessary to cause the apparatus to operate with a force f. This weight corresponds to a volume v = Now, as this quantity is necessarily the increase of the volume V of the reservoir for 1° of temperabeing the density of the mercury. v = V. a, ture, we shall have

a being the coefficient of the apparent expansion. of the mercury.

We deduce from this

V =

V =

m.f
d. 2 (m + 1)

The inventor was therefore led to give the mer- and finally-
JOHN M.
curial reservoir quite large dimensions, in order that
the weight of the volume expanded might have a
value capable of actuating the apparatus. We
shall calculate this value further along.
The thermometric reservoir V carries a tube, S,
of small diameter, which terminates in a volution,
the thermometers, other than acts with so much force in

BAROSCOPIC THERMOMETER.

U mercurial and alcoholic ones, have generally, whose spirals are so arranged that the whole

with the axis of rotation of the apparatus. This
arrangement was adopted in order to avoid giving
the tube too great a length, and also in order that
the centre of gravity may not be sensibly displaced,
whatever be the quantity of mercury contained in
the spirals.

The tube S is placed in a sort of gutter, Z, of
metal, which serves to support it, and which' is
fixed to a piece of metal, A, that carries the axis
formed of the two knives B, of steel or other hard
material, resting upon supports R, also of steel or
other hard material.

been based upon the principle of the deformation of
a body by expansion. The instrument that may be
regarded as the type of this kind is Breguet's
metallic thermometer. These apparatus all offer
the same inconvenience; after operating a certain
length of time, the dilatable body constituting the
thermometer undergoes, through successive twist-
ings, certain melecular modifications that change
the structure of it, so that the same variation of
temperature no longer affects it in the same way
that it did at the time that the apparatus was
graduated. The readings are therefore no longer
The height of the knives is sufficient to allow the
accurate, and the effects becoming marked in the
horizontal axis of rotation, constituted by the con-
long run, the instrument is put out of service.
The object of thermometers of this kind is to ob-junction of the knives and supports, to be situated
tain the displacement of a movable object (say a
needle) capable of being easily seen at a distance, or
to establish contacts with determined points. Now,
in order that the movable object may be capable of
being displaced, it is necessary that it shall be sub-
mitted to the action of an initial force, the result of
a change of temperature, and such force has
generally been sought in the deformations of some
substance.

The baroscopic thermometer is designed to overcome such irregularities of operation through the use of a motive force which, really invariable, always produces the same effects for the same

causes.

This force is gravity. In this apparatus there is utilised the weight of the volume to which the body expands; in other words, instead of employing, as an initial force, the breaking of the geometrical equilibrium of a body, we utilise the breaking of its static equilibrium in assimilating the expansible body to a balance-that is to say, to a lever of the first kind, one of the arms of which is formed of the expansible material, and the other of the expanded part of this same material. It is evident that, with

(2)

It will be seen from formula (1) that the difference of length of the arms is unfavourable in the sense that the weight of the quantity of mercury

portion as the ratio is greater; but this arrangement

has been employed in order to render the apparatus lighter, and therefore more sensitive. The maximum effect will be obtained with arms of equal length, for the weight p will then act with a force equal to 2p. In order to establish the graduations, taken as a basis-a formula that gives the tangent of the angle described by the beam for a given load. the temperature, it would be possible to adopt a Instead of a spherical reservoir of wide diameter, spiral reservoir that would be more sensitive. the mass of which requires a certain time to take Finally, in order to render the apparatus lighter, mercury might be left only in the long arm, and very expansible. But this arrangement would the reservoir might be filled with alcohol, which is it has been tried already without much diminish the precision of the instrument. Moresuccess.-Le Genie Civil.

the formula of the sensitiveness of the balance is

over,

THE PLANET MERCURY;

a little above the centre of gravity of the apparatus.
A regulating screw, M, placed at the upper part of
the piece A, permits of varying the sensitiveness.
In the centre of the spherical calotte formed by the
spirals there may be fixed either an indicating
needle, E, or any movable device capable of pro-
T the regular meeting of the Toronto Astro-
ducing contacts, if it be desired to use the thermo-
at a distance. However, the inventor is now put-A ton cefnd Physical Society, held early this
meter for indicating the variations of temperature
now of Detroit, of which the following is a summary,
ting the last touches on a very complete registering month, an interesting paper by Mr. D. K. Winder,
was read:-The sun, earth, and planet fell into
apparatus designed to be actuated by the thermo-
meter.
line at the predicted time on the evening of May 9,
and the planet Mercury had made a digit or two of
progress on its way across the solar disc before sunset
at Detroit. The low altitude of the sun and the
I therefore
unsteady condition of the atmosphere through
Martius rendered it certain that no observation
which views were obtainable from our Campus
determined to devote the few minutes available
of the moment of contact could be made accurate
enough to be of scientific value.
before sunset to an analysis of the spectrum of the

surface of the sun in close proximity to the position
of the planet on its disc. I am happy to record
what I hope will prove to be another triumph of the
spectroscope if it shall be corroborated by the
reports of other careful spectroscopic observers,
and teach us something regarding the constitution
of the atmosphere of the planet Mercury. During
the early part of the transit the spectrum of the
light received from the edge or limb of the planet
exhibited the telluric lines greatly intensified and
anusually dark. This appearance of the spectrum in-
dicates the presence of aqueous vapour in the atmo-
sphere of Mercury. The distinctness of the telluric
lines of the solar spectrum, due to the low altitude
of the sun at the time of the transit, rendered the
sonditions specially favourable for the revelation of
this interesting fact.
The result of this observation also shows that the
planet is surrounded by a dense atmosphere, which
a more attenuated state must extend two or

three hundred miles from its surface; otherwise the spectrsocopic results mentioned would not be seen at the great distance of Mercury from the earth.

lower guide is fitted a slide which is attached to an
adjustable form projecting rearwardly from the
lathe shears. To this slide is pivoted the upper
guide, which is widened at the end and provided
with a curved slot for receiving the bolt which
clamps it to the slide in any desired position. To
the upper guide is fitted a narrow sliding block,
which is pivotally connected to a bar, projecting
rearwardly from the tool-rest. This bar is accu-
rately fitted to ways in the carriage, so that it
causes the narrow sliding block to move with the
carriage. The upper guide bing set at the required
angle, the turning of the taper proceeds in the same
manner as turning a cylindrical bar, the sliding
block being moved inwardly or outwardly by virtue
of its engagement with the upper guide. By the
use of this attachment, tapers may be turned as
smoothly as cylindrical surfaces. Tapering holes
are bored by replacing the turning tool with a
boring tool and proceeding in the usual manner, the

attachment causing the tool to move toward or
away from the axis of the lathe, as may be required
to produce the taper.

SCIENTIFIC SOCIETIES.

ROYAL ASTRONOMICAL SOCIETY. TGeneral Tennant, president, in the chair. HE last meeting was held on June 12th, Richard Edw. Synge Cooper, of Hillmorton Paddox, Rugby, Hugh F. Newall, of Trinity College, Cambridge, and S. H. Ridge, of Melbourne, Victoria, were elected Fellows of the Society.

Mr. Knobel read a paper by Mr. H. C. Russell, director of the Sydney Observatory, entitled, "Notes on some Star Photographs recently taken at the Sydney Observatory." The paper was accompanied by prints of several photographs taken with a camera of 6in. aperture, and about 30in. focus, and with the 13in. photographic telescope with which the Sydney Observatory will join in the International Survey of the heavens. With both of these instruments photographs had been obtained of the n Argus nebula, one with an exposure of eight hours, and another with an exposure of five hours. Though a considerable extent of the nebula has been photographed, its light seems to be less actinic, and to act much less rapidly on the plate than the light of the great Orion nebula. On the other hand, Mr. Russell remarks that the light of many parts of the Milky Way in the Southern hemisphere seems to be very actinic, and that in many regions stars and nebulosity are photographed where the eye sees nothing with the telescope.

Dr. Gill said: I had the pleasure of examining Mr. Russell's photograph of the 7 Argûs nebula the other day, and I certainly never saw a more beautiful photograph of a nebula. Not only is there a great deal of nebulous detail shown, but the stars, down to the smallest, are represented by exceedingly sharp and well-defined points. This nebula is certainly very deficient in blue light, and photographs very slowly. On the other hand, there seem to be many regions in the Milky Way where the stars photograph very rapidly, and seem to be rich in blue light. This is very interesting in connection with what Prof. Pickering has published with regard to the brighter stars of the Milky Way being all of the Sirius type. We were at first very much puzzled to find the Milky Way stars in the Southern heavens showing a greater photographic magnitude than their eye-estimated magnitudes warranted. Their magnitudes as determined by photographs were generally half to three-quarters of a magnitude too great as compared with eye estimates. This might have been due to their being which might cause the eye estimates to be systemseen on a brighter background than other stars, atically too small, or it might be due to a difference in the nature of their light. Prof. Pickering's spectroscopic observations showed that the larger Milky Way stars were generally of the Sirius type, Now we find the smaller stars of the Milky Way having a photographic magnitude above that which would be indicated by eye estimates, and consequently they are probably blue stars. Therefore we probably have in the Milky Way a structure in the heavens which, according to the theory of the evolution of stars, seems to be a more recent structure than other parts of the heavens.

The spectroscope used was in perfect order, and
the dispersive power was sufficient to divide the
D lines of sodium and reveal one faint line between USEFUL AND SCIENTIFIC NOTES. and were rich in blue rays.

them.

The unsteady character of the atmosphere at my point of observation caused frequent variations in the darkness of all the telluric lines in view, but they certainly were always more distinct in the light received from the edge of the planet and from the dark body of the planet than in light received from other parts of the disc of the sun.

As it may be of interest to some members of the society, I shall describe the arrangement of the telescope and spectroscope. The image of the sun and planet was received upon a transparent screen attached to the telescope, and its course marked upon the screen as it crossed the field. A narrow slit was cut in the path traversed by the planet, to which the slit of the spectroscope was directed. By this arrangement it was possible to pass the slit of the spectroscope frequently over the planet and note the variations of the spectrum. This arrangement will be found useful in like observations by those who use alt-azimuth telescopes.

LORD'S TAPER ATTACHMENT FOR

LATHES.

THE largest farm in the world is in the State of Louisiana. It extends over 1,500,000 acres, and is 100 miles long and 25 miles broad. All the general work is done by steam. There is not a single draught horse on the estate.

photographs with a great deal of interest. The Mr. Ranyard said: I have examined Mr. Russell's larger photograph of the Argus nebula shows great extensions of the black rifts we were already acquainted with. There is one of them which is very striking, and looks like a dark branching tree on a bright background. I should like to remark, in connection with what Dr. Gill has been saying, that the Milky Way is a region of red stars as well as of blue stars. For example, in the region of the brought out streams of small stars over an area Coal-sack, when Mr. Russell's photographs have where the eye sees only blackness, there are several red stars which seem to be associated with blue in a cluster. Whether the photographing of these small stars is due to their blue colour or not it is difficult to say. It seems to me that everywhere the photographs reach a lower magnitude than can be reached by the eye.

A Real Newspaper Press List.-Not padded out with titles of bogus papers, and a lot of obscure periodicals which nobody but their publisher and the advertising-agent-who, for a big commission, keeps them going at the expense of advertisers can see, but embracing all genuine papers, and fairly stating their characteristics, the admirably got Newspaper Press List just issued by Messrs. R. White and Son, of 33, Fleet-street, the old-established Government advertisement contractors, should obtain a wide circulation. No advertiser can possibly select a better agent to intrust his business to, and very few are so thoroughly trusted and esteemed by all the leading newspaper-offices. Photographic Novelties.-We have received from Messrs. Taylor, Taylor, and Hobson a sample of a new level (No. 5) which they are introducing for cameras. One of these levels used on the side of a camera swingengine lathes, as ordinarily constructed, a back will be found useful in avoiding the of a lathe eccentrically with reference to the axis vertical distortion or of the lathe mandrel, and short tapers are someleaning which is often times turned by means of a slide-rest adjusted at a noticeable in photo- Dr. J. L. E. Dreyer read a paper on the "Proper proper angle. These methods, however, are unsatis- graphs of buildings. Another fixed on the back of Motion of Twenty Southern Stars." He said that factory, on account of the difficulty of adjusting the the camera-frame will insure the true horizontal it was interesting to note that no new star catalogue lathe so as to produce a taper of a given angle. placing of it. The new level is designed to be was nowadays published without bringing to light The annexed engraving illustrates improvement | placed low down on the side and back of the camera, the proper motion of several faint stars. If these designed for attachment to an engine lathe, which as the position on the top is sometimes inconvenient investigations are continued long enough, we shall admits of duplicating tapers on any angle without in the case of cameras on high tripods. The Fry get in time material which will enable us to make a regard to the length of the bar upon which the Manufacturing Co. send us some of their Compound much juster estimate of the true system of the stars. tapers are formed. It also provides for accurately Sulphokinone Developer in two solutions, which we Mons. Cornu was called upon to give an account boring holes for fitting these tapers. It is the have found excellent for developing negatives. It of his repetition of the Cavendish experiment for invention of Mr. L. L. Lord, of 936, Market-street, also yields very fine results in developing lantern-determining the density of the earth. At the Meadville, Pennsylvania. slides and transparencies, and works satisfactorily request of the President, he spoke in French. The The cross feed screw is detached from the tool-with the paper, opal, and ivory films manufactured torsion balance with which the experiments have rest, and to the carriage are attached a pair of arms, by this firm. It has the advantage that it can be been made has an arm of only 18in. long instead of which support the lower guide, which is arranged used several times, and it does not stain the fingers an arm of 6ft., as in the apparatus used by Bailey. exactly parallel with the lathe shears. To the of the operator. Balls of various material have been used-platinum,

The President: We must return our grateful thanks to Mr. Russell for these valuable photographs; and also, I think, to Sir Howard Grubb for the beautifully defining lenses with which they have been taken.

iron, copper, lead; and very many instructive researches have been pursued as to the small disturbing causes which affect the result. One serious cause of disturbance was got rid of by taking a wire to earth from both parts of the apparatus, so as to get rid of any difference of electrical potential. The rod on which the torsion balance swings, is suspended by a silver wire six mètres long. It was found at first that this wire was subject to continual changes. It had been unwound from a coil, and was therefore strained, and with changes of temperature its tension was continually changing. This difficulty was got rid of by passing the wire through a red-hot tube in a flame, and afterwards pulling it straight and slightly lengthening it. Slight differences of temperature even produced by the ray of light falling on the scale gave rise to air currents, which produced an effect similar to the effect produced by attraction between the balls. Recently, instead of moving the heavy attracting balls, mercury has been run into glass globes, first on one side, then on the other side of the torsion balance. Mons. Cornu believes that he can now measure an attraction corresponding to the two hundred-thousandths part of an milligram.

The Astronomer Royal showed some photographs which he had obtained of stars when making use of the wire gauze screens recommended by the Photographic Commission. These photographs were thrown upon the screen, and showed that there were spectra symmetrically situated around the image of the star. The Astronomer Royal thought that slight differences in the screens-for example, if they became bent-would give rise to variations of the amount of light in the central image as well as in the spectra, and that consequently they could not be relied upon as constantly reducing the light of stars through two magnitudes. The following papers were taken as read: S. W. Burnham, The companions to Regulus": G. E. Hale, "A Method of Photographing the Invisible Solar Prominences"; the Rev. S. J. Johnson, "Probable Early Observation of an Immersion of Titan"; F. McClean," Photographs of Metallic Spectra"; A. Marth, "Data for Computing the Positions of the Satellites of Jupiter, 1891, with Tables of the Inequalities"; A. Marth, "Ephemeris for Physical Observations of the Moon,

1891."

ROYAL METEOROLOGICAL SOCIETY.
THE
HE concluding meeting of this Society for the
present session was held on Wednesday even-
ing, the 17th inst., at the Institution of Civil
Engineers, 25, Great George-street, Westminster,
Mr. Baldwin Latham, M.Inst.C.E., president, in
the chair.

presented by Dr. J. B. de Toni as being the com-
mencement of a most important work upon the
marine alga. The portion now before them con-
tained one section only-the Chlorophyca, or green
seaweeds, every known species of which was fully
described. The other two great sections, the red
and the brown varieties, would be afterwards dealt
with, and the whole, when completed, would form
the most valuable work of reference on the subject
yet contemplated.

Prof. F. Jeffrey Bell referred to the book, "Les-
sons in Elementary Biology," presented by Prof.
Jeffrey Parker, of Otago, N.Z., as one likely to be
of interest, an extract from the preface being read
to show the aim of the author in seeking to assist
the amateur microscopist as well as the professional
student. Mr. Crisp's valuable donation of the last
volume published by the Palæontographical Society,
dealing with the echinodermata, ammonites, &c.,
was also referred to.

Mr. J. Mayall, jun., said he had much pleasure in presenting to the Society a copy of the English edition of Engel and Shellbach's optical diagrams, together with an explanatory volume by Mr. W. B. Hopkins, which he thought would prove of use to those who were giving attention to the passage of pencils of light through various forms of lenses. The original work was a recognised textbook in Germany and other parts of the Continent; but it had become very scarce and expensive. The English edition did not differ essentially from the original, though the diagrams were reduced in size, and in some cases, where the rays were symmetrical on both sides of the optic axis, they were figured on one side only. Prof. Shellbach's graphic treatment of the formation of caustics was recognised as the most perfect work of the kind known, and had long been commended by the leading mathematical opticians.

The President announced the death of Prof. P. Martin Duncan, who, as a past president of the society, was well known to most of the Fellows on account of the active and efficient manner in which he performed his duties during his occupation of the chair, and was equally well known to others through his great work on the Echinoderms. His death occurred on May 29.

the Society had not received a slide of that kind that
could be regarded as satisfactory for testing such an
objective.
Mr. C. L. Curties exhibited in its finished form Mr.
Nelson's apparatus for obtaining monochromatic
light, a specimen of Rhomboides being shown under
a dry in. objective.

Mr. Mayall said Mr. Curties had had the apparatus made entirely of metal, and had hit upon au inexpensive design, though the construction seemed rather too light to be steady enough for general use. He thought there was no absolute necessity to employ a high-class photographic lens for projecting the spectrum; any moderately good achromatic lens of suitable focus would answer the purpose. He understood from Mr. Nelson that for observation work with the microscope the optical combination at the lantern or slit end of the apparatus was not needed, the slit screen being sufficient; but for photo-micrography, by means of artificial light, this optical combination was important to increase the light. The apparatus was so devised that the microscopist might employ any prisms or photographic lenses he possessed. He thought the pierced cardboard on which the spectrum was projected would soon warp out of shape, and that it might be replaced with advantage by a metal plate coated white, which would retain its shape. If a prism had to be made specially, one of light crown-glass would probably answer better than the dense flint.

Mr. T. T. Johnson, exhibited and described a new student's microscope which he had devised.

Mr. Mayall said the special point was in the application of a screw movement instead of the usual rack-and-pinion to raise and lower the substage, the screw being in the axis of the bearings of the substage and tail-piece, and the actuating milled head projecting slightly at the back of the stage. He thought this was a very economical way of applying focussing mechanism to the substage. The position of the actuating milled head seemed to him most happily chosen for convenience, though it would probably be necessary to make the head larger so as to provide more grip for the finger, as the movement would be certain to become less free in course of time. When he saw the instrument on the previous day he pointed out that the mirror was connected with the substage and went up and down with it; this defect had since been corrected. He thought this substage adjustment would commend itself to notice, and that if it was not already registered it would certainly be taken up by other opticians for the less expensive forms of microscopes. It seemed to him that Messrs. Johnson had undoubtedly scored "1" by bringing out this screwfocussing arrangement for the substage.

Prof. Bell said that as the only officer of the society present who held office during the presidency of Prof. Duncan, he rose to give expression to the regret which he felt at the loss the society had suffered by his death. Prof. Duncan was one of the few remaining naturalists who was not a specialist. His early contributions to botanical science were succeeded by a very important contribution to geology, in which he not only dealt with fossils as Australia and elsewhere. such, but also in their relation to the fauna of The work to which the President had alluded was produced Mr. W. Johnson said the arrangement had been later on. His work as & Fellow of the Mr. J. J. Colman, M.P., Mr. E. B. Dukoff- Society was rather that of one of the older from himself. He had to thank Mr. Mayall for devised by his son with very small encouragement Gordon, B.A., Mr. G. E. Leon, Mr. T. de C. Meade, microscopists who laid great stress upon the use of Assoc.M.Inst.C.E., and Mr. F. Russell, F.R.G.S., the lower powers; but the appreciation in which he calling his attention to the mistake of connecting Mr. A. J. Hands, F.R.Met.Soc., gave an account was held was best shown by the fact that the recognised the error the moment it was mentioned,

were elected Fellows of the Society.

of a curious case of damage by lightning to a church at Needwood, Staffordshire, on April 5, 1891. The church was provided with a lightning conductor, but Mr. Hands thinks that when the lightning struck the conductor a spark passed from it to some metal which was close to it, and so caused damage to the building.

Mr. W. Ellis, F.R.A.S., read a paper on "The Mean Temperature of the Air at the Royal Observatory, Greenwich, as Deduced from the Photographic Records for the Forty Years from 1849 to 1888," and also gave some account of the way in which, at different times, Greenwich mean temperatures have been formed.

ordinary by-laws of the Society were suspended in
order to keep him in office for a longer period than
usual. Those who knew him personally would feel
regret that there had passed away from among them
one whom they could not meet without feeling the
happier for the meeting, and it would add to the
regret of those who thus knew him in health to
his decease in a condition of almost intolerable
know that he lay for many months previous to
suffering. His name would be remembered with
affection by all who had come intimately into

association with him.

want of sharpness was due to the employment of a
projection eyepiece for a tube-length of 160mm.,
whereas the objective was made for a tube-length of
180mm. The illumination was axial with a Zeiss
achromatic condenser of 1.2 N.A. Mr. Comber
thought the resolution showed indications of so-
called "beading," and hence he inferred that the
ultimate resolution would be shown to be similar to
that of its congener Amphipleura Lindheimeri. The
mounting medium had a refractive index of 2-2, but
was very unstable, granulations appearing in a very
short time. The negative showed these granu-
lations, though the object had only been mounted

A negative of Amphipleura pellucida, recently produced with Zeiss's new of 1.6 N.A., and sunlight, by Mr. T. Comber, of Liverpool, was exMr. Ellis also read a paper on "The Com-hibited, and his letter was read suggesting that the parison of Thermometrical Observations made in a Stevenson Screen with corresponding Observations made on the Revolving Stand at the Royal Observatory, Greenwich." From this it appears that the maximum temperature in the Stevenson screen is lower than that of the revolving stand, especially in summer, and the minimum temperature higher; whilst the readings of the dry and wet bulb thermometers on both the screen and the stand, as taken at stated hours, agree very closely together. Mr. W. F. Stanley, F.R.Met.Soc., exhibited and described his phonograph, which is really a new form of chronograph designed for the purpose of ascertaining the distance of a gun from observations of the flash and report of its discharge by the difference of time that light and sound take in reaching the observer. The instrument can also be used for measuring the distance of lightning by timing the interval between the flash and the report A paper was also read by Mr. A. B. MacDowall on "Some Suggestions Bearing on Weather Pre

of the thunder.

dictions."

two or three days.

Mr. Mayall expressed his surprise at the want of sharpness in the definition, especially as the manipulations were conducted by so careful and accurate a microscopist as Mr. Comber. He regretted that Mr. Comber had not had a projection eyepiece corresponding precisely with the tube-length of the objective, so that his trial of that particular objective might have been regarded as authoritative. This was the more regrettable from the fact that so few microscopists in England had their photomicrographic apparatus installed for use with sunlight. The difficulties involved in obtaining suitobjectives of 16 N.A. were very great, due, as he understood, to the chemical action of the dense mounting medium on the flint-glass covers. So far

the mirror with the adjustable substage. His son

and at once removed the mirror to a separate

sliding-piece.

The President said they were favoured by the presence of Dr. J. E. Talmage, of Great Salt Lake City, U.S.A., a recently-elected Fellow, who had not only made a special effort to attend the meetspecimens of organic life found in the lake, which ing, but had also brought and exhibited some he would describe.

Dr. Talmage, having expressed his thanks to the President for the kind way in which he had introduced him, and also to the Fellows of the Society for the cordiality of their reception, said that he left Salt Lake City rather hurriedly in order to avail himself of the opportunity of being present at the meeting. On this account he had not brought over so many specimens as he could have desired, but he had placed under some microscopes in the room several examples of the brine shrimp, Artemia fertilis, from the Great Salt Lake, which he thought might prove of some interest. He had also prepared a "Note on the Occurrence of Life in the Great Salt Lake," which he read to the meeting. He found these objects rather difficult to mount for It was, for instance, permanent observation. almost useless to use glycerine, because it rendered the structure indistinct by transparency. He had at present discovered no way better than by putting

them into some lake water with a 5 per cent. solution of alum. The structure was also so very delicate, that it was very difficult to spread them out upon a slide, but by the use of the medium named the creature could be transferred to the slide and spread itself out as it died. In addition to slides of these shrimps, prepared in the manner described, he also exhibited specimens of the calcareous sand from the lake shore.

Prof. Bell said a paper was read at the February meeting, in which Dr. W. B. Benham described a new earthworm from Central Africa under the name of Eminia Equatorialis. It was found some time appropriated, Dr. Hartlaub, of Bremen, having given it to a bird previously found by the Emin Pasha Expedition. In a letter received from Dr.