ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1353. [73851.]-Micro-Photographs.-I am desirous of taking micro-photographs, and cannot succeed in obtaining a fine enough grain. The ones I have taken, which were by the wet collodion process, when examined with a lin objective, appear so coarse that the fine detail is lost. Will anyone kindly inform me what collodion will answer to give a microscopically fine image, and formula for developer for same, and name of any book on the subject?-MICRO. [73852.]-Iron Cell-I have been trying Bennett's iron cell, but have not been able to obtain any current. I should like to know if it matters if the iron filings are put under or around the zine; also how much caustic potash or carbonate of soda to a quart of water ?BENNETT. [73953.] Rope Splicing.-Would any reader give me any information in rope splicing? The long splice in six stranded wire rope preferred. I understand the laying of strands, but I am beat with running one strand into the other.-J. W. [73854]-Two Large Bichromate Cells.-Would Mr. Bottone kindly say their probable E.M.F. and constancy for experimenting, which I have made? Sizes as follows:-Cut gas carbons, two in each, 8in. long, 2in. wide, in. thick, one zinc same size, in: thick, jar contents three pints. Would they work small dynamo motor, size as given in your book, or what c.p. lamp would they light? If by adding one extra carbon and zinc in each cell, say, 8 carbons, 2 zincs, would the gain be worth doing-if so, how should they be connected up? SOMERSET LAD. [73855.1-Plug Cocks.-How are plugs of small cocks for model work bent so as to make plug and handle in one, as I tried to bend the brass when it was turned, and it always broke? when hot, and they broke also. Also what description of I heated the brass and cooled it; drill is best for boring the taper hole in cock?-AMATEUR. 173856.]-Surveying. What is the limit of error tolerated in this country in measuring with the chain? I find it stated by Col. Sir Charles Wilson, in a paper read by him a few days ago at the Society of Arts, that the limit of error allowed by chain surveyors on the tertiary triangles of the Ordnance Survey to be two links in 1,000. (I presume he means 1-500). I should be glad to know if this is the usual practice. What are the limits allowed in measuring angles? It might interest other readers besides myself to know more about the field work of the Ordnance Survey. What are the primary and secondary triangles. Tertiary triangles are those having sides about one and a half miles in length.-FOGHORN. [73857.)-Box Sextant.-I should feel obliged if some reader would inform me how to put a box sextant into perfect adjustment.-FOGHORN. [73858.]-Meridian Mark.-I want to find my meridian. Can I do so by the list of star transits given in Astro. Notes! As near as I can determine, I am 1m. from Greenwich on the map, but by comparison maps do not seem accurate. What way can determine my position accurately? I may say that I cannot get the sun only for about 1 hour after noon. time to within a few seconds.-J. E. B. I want to obtain Greenwich [78859.1-Dynamo.-In driving a dynamo with H armature, is most of the resistance due to the induced current? Is the resistance greater than with the drum type, on account of the induced current magnetising the armature, or can it not affect the magnetism of the armature by the field-magnets, as it results from that magnetism?-H. A. [73860.]-Telephone Stations.-To MR. Allsop.In reply No. 71288 in issue of May 2nd, 1890, you give connections for telephone. I perceive that in the speaking circuit both batteries come into force. Can the connections not be arranged so that only one battery comes into circuit, as I am afraid, for the distance I have, the battery power would be too strong? I wish to experiment with a Gower transmitter and a Bell receiver, and would be obliged if you would kindly tell me the following: Does it matter about the pieces of carbon in transmitter being coppered? Need the pieces of brass and centre carbon be insulated from the diaphragm; How must I fasten the pieces of brass and centre carbon to the diaphragm (it being so thin)? Should the diaphragm be fastened all round the edges, as I am afraid of its warping. and would it improve the microphone if diaphragm were fastened into cover of containing box on thin pieces of rubber?MICRO. MALARIA is unknown in New Zealand, but prevails in North Australia to as far south as 17° lat. IN America some passenger cars are made entirely of steel. The frames are built of angle, channel, and T-steel, and the interior is lined with thick felt. A mass of springs in the platform of the car is intended to deaden the force of the impact. The Rhythmic Action of the Heart.-From some researches made by Dr. Hamel, under the direction of Professor Kronecker of Berne, on the circulation and the pulse, some new facts have been added to our knowledge on the subject. The vascular system of animals (frogs and crabs) was connected with it was then found that the more nearly the an artificial heart, and natural condition of intermittent pumping was imitated the more blood could be driven through the vessels. When continuous pressure was employed, less blood was caused to circulate; but, on the other hand, there was a greater tendency to injury of the vessels, permitting exudation of fluid into the surrounding tissues, and thus causing cedema. It would appear that the elasticity of the arteries is kept up by the rhythmical dilatation they undergo. Henricius and Kronecker have also shown that the regular movements of respiration act as a kind of beneficial massage on the heart muscle, and it is suggested that the rhythmical movement of the pulse may act in the same way on the arterial walls. -Lancet. ANSWERS TO CORRESPONDENTS. of the ENGLISH MECHANIC, 332, Strand, W.C. HINTS TO CORRESPONDENTS. for illustrations on separate pieces of paper. 2. Put titles the general good, and it is not fair to occupy it with The following are the initials, &c., of letters to hand up J. MASON.-A. Henry.- Waterloo.-T. FEB. 27, 1891. Wanted Column at the price stated.)-Jor. (Do not understand you. Platinum in sheet and wire is to be bought, though the price may be high. You do not put any definite query. Is it that you cannot procure platinum. that you do not know how to affix the connecting pieces, or what?)-E. BAILDON. (They are generally cut from hard pieces of lime, and then rounded into the required shape. Chalk will do, or the limes can be moulded up; but as a rule the latter crumble quickly.)- Susi. What you appear to have is a die, which you can use as (Do not understand you. a seal, or, if you have the counterpart and a press, for embossing.)-W. A. S. (Please see the indices, or look through recent numbers.)-HENRY THOMAS. (We suppose you mean the patent silvering; but in that the solutions are generally used warm. See indices, however.)-ALFRED BALDWIN. (It is not likely the glass will stand much more. 2. The other query is probably replied to this week.)-BROOKLYN BRIDGE. (We suppose it is because the material is different. Simply rub over with white wax when warm; but if spotted, it is doubtful if it is good meerschaum.)-AMATEUR, R.0.8. (The pulsion telephone was described and fully illustrated in the number for Jan. 17, 1890.)-MUSJID. (Rossiter's "Dictionary of Scientific Terms," published by William Collins, may suit you; but for medical terms procure Hoblyn's Dictionary, published by Whittaker and Co.)-W. W. (An examination question. Do you not attend a class?)-W. R. (See indices. You mean the clock to start an electric bell, we presume. Several plans in back volumes. You must use some sort of time-measurer to ring at "any stated time.")-SIGNOR. (Have not the details been given many times? See the indices to be published shortly, and look through Vol. L. and other volumes for a variety of dynamos.) degree of polish required. - DAVID. (Depends on the You powder, crocus, or even rouge.)-M. B. (Any of the try puttytool-shops in, say, Clerkenwell, can supply you with drills required; or no doubt any of our advertisers who deal in tools and steel wire could supply you. A diamond drill would go through. 2. Softening can be accomplished by making red-hot at a soaking heat, and then cooling very slowly. You ought to succeed by burying them in lime, but you must give them time. As you have so many, why not get some one with suitable appliances to do them? Do you want them hard again?)-C. D. (Yes, it is said to be efficient as a filter; but will not Clark's process do for softening the water? It consists in adding lime cream to the water, and allowing it to settle. The water should be analysed, and the analyst will tell you how to soften it. indices.)-G. S. (Are you sure it is silver, or quickSee silver? If the latter, the mercury may be recovered by distillation, but it is doubtful whether it is worth while unless the quantity is very large.)-AUSTRALIA. do not know of any small petroleum motors; but if they are made, perhaps those who make them will advertise when they find there is a market for them.)-MELBOURNE. (We cannot give any further information about the process. As you will see, it is announced as a sort of secret process. Asphaltum is a black, hard, glossy variety of bitumen, and in the process is used to protect parts of the plate from the action of the acid. 2. Depends on the size and the amount of charge. Slowly only: it is current, not sparks.)-INQUISITOR (Saint's sewing machine was patented in 1790; but whether "a sewing machine" was invented from a carl machine we do not know. The first commercially successful machines were those of Elias Howe. can (We Hunt had preceded him by several years, and sold machines in New York, but did not follow up the business.)— DRAUGHTSMAN. (Why not try with a waste piece? But we suspect either drawing or tracing cloth will be spoilt.)-ASHTON. (We do not think it matters in the least which. And we think any real benefit you are likely to derive from either is nil. !)-E. T. CARTER, T. SHELDON (In type). Mr. Harness Electropathic Belts. They cure all rheumatic Book t CAERLEON. (No very high pressure is required in a coil of pipe when steam is used to heat water, for the greater number of heat-units are obtained when the steam is condensed into water. The defect is plain enough, and the remedy too-there must be a greater length of pipe for the steam to pass through. But why not adopt the usual method, and heat the cold water by means of a furnace boiler?)-C. A. HARTLEY. (The method of propelling boats by means of steam-jets has been debated in our columns many times, and there is a toy steamboat worked by such means; but the paragraph referred to mentions that a paper was read by Mr. Green on the lifeboat fitted with the water-jet propeller-not "steam-jet." The motive-power employed is steam. The idea is old, and was tried many years ago in H.M.S. Waterwitch, but not with so much success as to encourage the Admiralty authorities to go further. The whole subject has been discussed at length in back volumes. Do not answer letters of any kind through the post. See "Hints" above.)-A. PEERLESS. commended in the Syllabus; but Huxley's works (Books are reshould certainly be taken for that exam.)-W. B., Seirnton. (Nominal horse-power is an absolutely useless term, except in trade, when a cylinder of so many inches capacity is said to be of so much nominal horsepower. The actual horse-power depends on the pressure of the steam in any given cylinder, and the speed at which it drives the piston. 2. No difference, except that of pressure. Nowadays 80lb. would not be considered "high" pressure. The "distinction" is in the build and strength. 3. There is no definite rule for calculating the actual horse-power of boilers. About 15sq.ft. of heating surface per horse-power is a rough and ready rule. Please see indices of back volumes.)OLD SOL. (Do not think you can make globes " cheaply," unless they are manufactured in considerable numbers. We do not know where the maps suitable for pasting on them can be obtained; but no doubt an advertisement in the Wanted column would bring the desired information.)-J. WESTWOOD. (What do you mean by a "panorama"? Some are the usual painted canvas unrolled from one spindle to another. "Book of the Lantern" can be obtained from any book2. Hepworth's seller.)-ASHTON. (It will not make the least difference as to the efficacy of the belt, whether the wires are interlaced or not.)-999, Winchester. (Yes, if made strong enough to stand a pressure of, say, 100lb., and also (2) if it enough for the two engines. 3. Certainly if the tincture of iodine consisting of 1 gramme of iodine would Iodine and Hydroquinone.-According to generat- steam fast Dr. Eder, in the Photographische Corresponder, a communication from one to the other is always per- in 50c.c. of alcohol, and diluted with 50c. c. of water, fectly free. It is usual in such cases to put the safety-produces an extraordinary effect when added to the valve on the connecting-pipe instead of on one of the boilers.)-W. (Try Spons, 125, Strand. They publish books of the kind; but there are many recipes for 40c.c. of developer causes the image to appear hydroquinone developer. liqueurs and cordials in Cooley's Cyclopaedia," which almost instantaneously. The contrasts appeared Three to six drops in is published by J. and A. Churchill.)-AN OLD READER. much softened, and a weak image often results (Electric Bell, Light, and Telephone Fitting have been when the exposure has been instantaneous. fully described in recent volumes.)-NEW READER. (Unless you have many to do, it will be cheaper to hand over the fittings to those who do such work. They must be thoroughly cleaned and polished, then made warm, and the lacquer applied with a soft brush in straight strokes-once only. 2, &c. See indices, or watch issuing numbers. Cannot repeat such replies every week.)-DIM SIGHT. (There is an operation for cataract, but a skilled surgeon is required to perform it. In the alleged cures by medical treatment the disease probably never existed.)-ELECTRICAL STUDENT. (Such insertions may be ascertained on application to the Publisher. books are being continually recommended, and certain works are actually specified in the Syllabus as suitable.) -E. C. LESTER. (A small steam-engine would be the best, perhaps, unless a gas-engine or a turbine is available. See many replies, in recent numbers, and the index which will be published shortly.)-J. L. (It depends on the size of the magnesium ribbon; but roughly, it burns very quickly. The powder is used for flashing," as it burns at once. The experiment should be made under the conditions required, which are not stated.)-J. L. (They work on the same principle as the lamps used by the costermongers. A cheap, inflammable oil is employed, and is forced through a coil of heated pipes to the burner-compressed air or gravity being used as the "force.")-JAMES BALL. dealer in "grindery" appliances, &c. See "Hints" (Of any above. Such queries cannot be inserted except in the 80 CHARGES FOR ADVERTISING Every Additional Eight Words: 0 Front Page Advertisements Five Shillings or the first 40 word afterwards 9d. per line. Paragraph Advertisements One Shilling S line. No Front Page or Paragraph Advertisement inserted for than Five Shillings. Reduced terms for series of more than ADVERTISEMENTS in EXCHANGE COLUMN-for Twenty-four Words For every succeeding Eight Words:: Sixteen Words For every succeeding Eight Words " 0 0 ice It must be borne in mind that no Displayed Advertisements for. insure insertion in the following Friday's number. The English Mechanic this joint wire will not be a very difficult job steel wire, fairly stout, and the bells are if the bar is slotted first. Another way is to AND WORLD OF SCIENCE AND ART. up the hammer-stems as shown in Fig. 84. A are eight slots, in which the hammer -2/4 FIG. 83. The part A is brass, the stem is round steel The hammer-heads are screwed tightly on The modern idea is to make the hammerheads of brass; they used to be made of steel. Brass gives a comparatively soft tone-steel a sharp, clear ring. Personally, I prefer the steel tone, in spite of the almost universal practice nowadays of using brass. The hammer-springs are screwed to the frame, and set by a second screw just below. By this means the pressure can be regulated to a nicety. If preferred, the springs can all be cut from one sheet of brass in the form of a comb. The tails of hammer - stems must be hardened and tempered, and rounded off as shown in Fig. 83, and finished off with a high polish. The stems must be quite upright, and all in a straight line. They "bank " up against Fig. 84 A stems work. These are kept up by means the bottoms of the slots in which they work, Fig 81. When the entire hammer work is done, the corners of the back and front plates must be cut away, as shown in Fig. 81, to such a depth as to allow the tails of hammers to come within about in. of the surface of chimingbarrel, and the bar must be "canted" slightly to insure that the hammer-tails point to the centre of barrel. The next thing is now to fix the bells themselves. The exact size of bells is a matter of fancy. Large ones, of course, give a more powerful tone; but I would warn readers that powerful tones are of no use in a small case. Indeed they are not heard as well as smaller bells would be. Therefore, unless a fair-sized case is contemplated, I should not advise is fixed to A by two screws, as shown. By more than 3in. or 33in. bells. This size, of this arrangement the whole of the hammer-course, refers to the largest. work can be removed on unscrewing the bar Fig. 85 shows how bells are fixed. The A from the plates. A reference to Fig. 48 (p. 303 of Vol. LII.) will show that the chiming-barrel was made separated by means of small wooden nuts between each, and are all tightened up by a nut on the spindle inside the smallest bell. Great care must be used in handling the bells, for they are easily broken. They must be adjusted so as to bring the edges all within 1ĝin., as shown in Fig. 86, which is mark the surface with a steel point, exactly opposite each hammer-tail (the shoulder of front pivot being in contact with the front plate). Then shift the barrel till back pivot rests against the back plate, and again mark the surface opposite Nos. 3, 4, 5, and 8 hammers (No. 1 strikes the smallest bell). These last four are used in the "Westminster" chimes. Clocks striking the hour on No. 8 bell use Nos. 2, 3, 4, and 7; but in this clock, $19 82 678 PLATE Fig 88 as a separate gong is used for striking the hours, the first method is to be preferred. Having done this, centre barrel in the lathe, and with a pointed cutter trace circles round it at every mark made, making the last four (Nos. 3, 4, 5, and S for "Westminster" chimes) deeper than the others, to distinguish them more readily. The hammer-stems are made of flat steel about in. wide, as in Fig. 83, and are all standards, A A, may be made either of brass pivoted on one wire passed through the bar or steel, though steel is more usual. A (Fig. 80). The drilling of the hole for spindle on which the bells are fixed The surface of the barrel must now be divided into five exactly equal portions. Those who possess a dividing plate can do this very easily. Those who do not had better cut a strip of writing-paper as long as In Fig. 90, the numbers refer to the The chiming-barrel makes two revolutions explained the elements of astronomy, so far every hour. Thus, at the first quarter, No. as they are needed in the work of the sur1 peal is used. At the half-hour, Nos. 2 and veyor. The chapters on Geodetic Astro3. At the three-quarters, Nos. 4, 5, and 1. nomy, on tacheometry, and on CurveAt the hour, Nos. 2, 3, 4, and 5, making two ranging with transit and chain will be found complete revolutions. very useful, even in this country, while it must be remembered that in Canada and Australia a diploma is needed before a man can qualify as a land surveyor. The book is freely illustrated with plates and diagrams, and as there are nearly all the tables of the ordinary kind, together with descriptions of the instruments, it forms an important addition to the series of Textbooks of Science issued by Messrs. Longman. In fact, it is a library in its itself for the young surveyor. Geometry of Position. By ROBERT H. GRAHAM. London: Macmillan. So far as the English language is concerned In fixing the bells great care must be this is the first work issued on the science taken that the standards, &c., are all quite which the French and Germans call geometry firm. Also the small wooden washers of position, which since the invention of between the bells must be tapered to a graphic statics has been made a subject of small edge, and enter the hole in each bell compulsory study in many of the Continental when screwed up tight. There should be institutions. In such works as Salmon's no metallic connection between the steel" Conic Sections " and "Higher Plane spindle and the bells. There must be Curves" some chapters deal with similar 4 wooden washers under each outside nut. Any neglect in these particulars will cause jarring in the chimes. the circumference of barrel, and divide by means of a rule or compasses; then, placing the paper round the barrel, mark the latter with a sharp point. At each division draw a line along the barrel from end to end, perfectly parallel to 2 3 The pin-holes are drilled at each point indicated, for steel-wire pins full in. in thickness. The pins project a shade over in. from the surface, and are shaped as shown in Fig. 89. The curved faces must be nicely polished. REVIEWS. problems; but this work is the only textbook, and the author has endeavoured to popularise a useful branch of geometry by illustrating its application to such problems as finding most economical sections for rails and girders, and the relative angle. of advance of the expansion over the main eccentric arm in valve-gear design. The work should certainly be studied by all who are interested in geometry and those professions connected with the constructional arts. A Treatise on the Law and Practice relating to Letters Patent for Inventions. By ROBERT FROST, B.Sc. London: Stevens and Haynes. Mixed Metals, or Metallic Alloys. By ARTHUR H. HIORNS. London: Macmillan and Co. THE HE author of this work is the Principal at the School of Metallurgy, Birmingham and Midland Institute, and, as he says, "living and working amongst Birmingham people," the metallic alloys naturally claimed much of his attention, for Birmingham is the centre of those trades which use the mixed metals. With the exception of articles THIS work, which is dedicated by permission in certain of the large works on Metallurgy, to the Attorney-General, is an attempt to Guettier's seems to be the only manual bring within reasonable compass the law as mainly devoted to a study of the alloys; but it at present exists in reference to letters Mr. Hiorns has, we think improved on that, patent for inventions, a complete his ory of and given in a handy form a volume that legislation in connection with the subject will be welcomed by all who work the metals, being too much for the size of even a legal whether separately or alloyed, for he seems textbook. Former practice has been referred to have gone to the best authorities for in- to when necessary to explain the present formation, and has made experiments of law, but the practice of foreign countries is The properties of the metals omitted. The various points are carefully themselves are described at sufficient length set out and judgments quoted to show the in an introduction; and then the alloys are practice, while there is a long table of cases taken up, commencing with those generally and references to them in foot-notes. An known as the copper alloys, which are, appendix contains the Acts now defining perhaps, of the greatest importance in the the law; the International Convention for arts and industries. Several valuable tables, the protection of industrial property; the 5 with the names of the authorities, are given; rules, forms, orders, &c., while a copious and besides the descriptions of the alloys, index completes a work which may be said there is much useful information in connec- to be a complete guide to patent law, so far tion with their actual production and as it can be compressed into about 800 pages. working, including diagrams of furnaces and An Introduction to the Study of Botany.other appliances. In short, Mr. Hiorns has, we imagine, given all the available information, and has produced a work which will be of great value to the practical metallurgist and the foundryman. its arbor. Then, assuming Fig. 88 to represent one division, mark all five on the barrel in a similar manner. That is, draw eight lines parallel to the arbor in each division: this will make in all 40 lines, in five sets of 8, with a space between each. Taking the "Westminster" chimes first, they are as follows: (1) 3, 4, 5, 8. (2) 5, 3, 4, 8. (3) 5, 4, 3, 5. (4) 3, 5, 4, 8. (5) 8, 4, 3, 5. The prefixed numbers refer to the divisions in barrel and read to the right, or as in Fig. S9, which is a front view. The chimes on eight bells, erroneously called "Cambridge" chimes, have no fixed order, but can be varied according to fancy. A good combination is as follows:(1) 1, 2, 3, 4, 5, 7, 6, 8. (2) 1, 2, 7, 5, 3, 4, 6, 8. (3) 4, 3, 2, 1, 5, 6, 7, 8. (4) 1, 3, 5, 7, 2, 4, 6, 8. (5) 6, 5, 3, 7, 2, 1, 4, 8. his own. Preliminary Survey and Estimates. By By EDWARD AVELING, D.Sc. Lond., Fellow of University College, London. London: Swan Sonnenschein and Co. THIS work has already appeared in our own. pages, and needs therefore little recommendation from us. We know, from the reception it met with while publishing in serial form, that no one could have performed his task better than Dr. Aveling, and we are sure that many readers will be glad to possess the handsome volume which contains the papers. A useful glossary of over 600 words is added. To the surveyors of this country engaged within its limits, this work will not appeal with much success; but to those younger men who are emigrating, and are not wedded to old practices, it is an excellent treatise, and one that will prove of immense use We have also received Heat as a Form in a new country. utilised the teachings and practices of William Heinnemann), which is the third of The author has Energy, by ROBERT H. THURSTON (London standard authorities on both sides of the the series of scientific handbooks issued by Atlantic; but while dealing briefly with that publisher. Not even the distinguished methods to be found in older textbooks, he Director of Sibley College can find much that has dealt at considerable length with such is new to say on the subject; but he has here subjects as tacheometry (telemetry), compu- traced in popular language the rise and protation by diagram and slide-rule, signalling, gress of the science which we now call and some others hardly known to the pupil heat. To those who know Prof. Thurston surveyor in this country. He has even abilities we need say no more.Elementary 66 Systematic Chemistry, by WILLIAM RAMSAY, F.R.S. (London: J. and A. Churchill), is an introduction to the study of chemistry for use in schools and colleges, in which Prof. Ramsay has attempted, by grouping and classification, to avoid the enormous number of apparently disconnected facts which often discourage the young. The method adopted will commend itself to many teachers.--Photography in a Nutshell, by the KERNEL" (London: Iliffe and Son), is a little work containing practical hints, notes on procedure, &c., for those already acquainted with the rudiments. Besides diagrams, it is illustrated with some specimen prints. Evening Work for Amateur Photographers, by T. C. HEPWORTH, F.C.S. (London: Hazell, Watson, and Viney, Ld.), is a work which deals not so much with photography itself as with the accessories lantern-slides, frame-making, magnesium lamps, electric battery, &c. The amateur will find it useful and readable. -The Art of Retouching, by J. HUBERT (London: Hazell, Watson, and Viney, Ld.), is a practical treatise on the art of retouching, which requires something more than mere skill in handling the "tools," -Learned Men's English: the Revisers, by G. WASHINGTON MOON (London: George Routledge and Sons, Ld.), is a combined edition of Mr. Moon's two works on the English of the Revisers, and will be followed by another combination of two works on the English of the Grammarians. -The Design of Structures, by S. ANGLIN, C.E. (London: Charles Griffin and Co.), is a work on the building of roofs, bridges, &c., which will be appreciated by students of engineering and architecture, especially as the author gives practical examples, besides explaining the theoretical points. Graphic statics forms pro horn washers, and thus produces a hermeticity which is rigorously absolute. Against the horn washer cl which is perfectly smooth bears a producing a first circumferential line of contact metallic valve S of concave form, the concavity with the horn, and, when the internal pressure acts on the valve, a surface contact which increases in direct proportion to the pressure exerted. By this combination of parts absolute hermeticity is effected, while the horn washer is indestructible, and there is great sensitiveness to the blow by which the valve is sub one of the subjects, and the work may be issue for 1889.) This is indisputable evidence | cartridge case the caoutchouc washer enters a recommended as containing much informa- of the very rapid advance of the electrical conical part b1 formed at the rear end of the case. tion in a comparatively small compass-500 industries. The book has been brought well This cone imparts its form to the caoutchouc and pages.- -Railway Appliances, by JoHN up to date, and contains many features of WOLFE BARRY, M.I.C.E. (London: Long- great interest to the electrical and allied mans), is the sixth edition of a well-known fessions, more especially a digest of the law textbook, with the addition, as an appendix, of electric lighting (specially written), a list of the "Requirements of the Board of of central stations in the United Kingdom for Trade." It is an epitome of the whole sub- the distribution of electricity, a list of ject. Lessons in Applied Mechanics, by electrical railways and tramways, a summary JAMES H. COTTERILL, F.R.S., and JOHN of the leading electrical events of the past HENRY SLADE, R.N. (London: Macmillan), year, information relating to the obtaining is, so to speak, "made up" from Prof. of Letters Patent, a complete list of the local Cotterill's larger work; but the portions authorities of England, and a reliable selected have been rearranged and rewritten biographical section, containing interesting in fuller detail, so as to form a work of more sketches of the careers of the leading living elementary character to meet the needs of electrical notabilities. junior students, and to serve as an introduction to the larger work. Mr. Slade is mainly responsible for the preparation of the volume, and he has produced an excel- GIFFARD'S CARBONIC ACID GUN. lent textbook. Celestial Motions, by sequently opened. In the modification shown in Fig. 1bis the valve has a central projection r with its side inclined from 1 to 2. The horn washer is dispensed with, and the caoutchouc washer c is made thicker. Two lines of contact between the valve and the washer are obtained, с namely, at y and z. The valve S in both modifications carries a strong coiled spring S1 fitting WILLIAM THYNNE LYNN, B.A., F.R.A.S. THE Giffard carbonic acid gun has been at its rear end on the valve and at its front end previously described and illustrated (see to the centre of a metal guide, D, which bears (London: Edward Stanford), is the seventh p. 115, last volume), but it is obvious that bears against a shoulder formed in the edition revised of a well-known introduction such a gun requires special appliances for cartridge case. The metal guide D has a to a study of the "most fascinating of the charging the cartridge cases, and the annexed central hole for the passage of the gas. sciences." Elementary Mechanics, by illustrations show the apparatus for the purpose The cartridge-case is cylindrical internally, and EDWARD P. CULVERWELL, M.A. (London: patented by M. Paul Giffard, of Paris. The has a conical part, T, in front of the valve Longmans), is a useful work for students cartridge-case is formed of a bar of hammered chamber, this conical part being for the object either at home or at college, as exercises are soft steel of great strength, having, for example, of facilitating cleaning, so as to remove small given. The author, who is a Fellow and a resistance of 80 kilogrammes per square milli- filings or other matters which may get into it. tutor of Trinity College, Dublin, treats mètre, and capable of an elongation of 20 per The interior of the cartridge case is strongly cent. without rupture. This bar is bored into nickelled, and thus made inoxidisable. Referring Statics before Kinetics, and adopts some the form shown at A in Fig. 1. Its front end is to Figs. 2 and 3, which represent the apparatus other reforms, which do not detract from the closed by a cap, a, of the same steel screwed and whereby the cartridge case is charged with the value of his work, but are undoubtedly of soldered thereon. Its rear end contains the parts liquid carbonic-acid gas, R (Fig. 2) is a reservoir assistance to the student.Ventilation, by for charging and discharging the liquid gas. of iron or bronze filled with carbonic-acid gas, WILLIAM PATON BUCHAN (London: Crosby These parts comprise a steel stopper, B, with a which is pumped therein through the channel C, Lockwood and Son), is a treatise on the central square hole wherby the screwing and un- or produced by chemical reaction. The inlet and practice of ventilating buildings, which, screwing of the stopper are effected without outlet valve is constructed in an analogous according to the author, "has been so sadly affecting the external form, which is essential, manner to that of the cartridge case already and foolishly neglected hitherto." The volume having regard to the important action which it described. The stopper B screwed into the contains a number of diagrams, and will be fulfils in the charging of the liquid gas. This thickness of the metal carries two washers of useful to the practical man.The "Elec-metallic stopper carries upon a cone on its inner two-thirds hardened caoutchouc forced into the trician" Electrical Trades' Directory and Handend a washer c of rds hardened caoutchouc, and conical part b1. The bronze valve S of concave against this washer is placed a washer c1 of black form is forced against the second washer by the book for 1891. (London: Electrician Office.) Siamese horn, which fits for only half its thickness coiled spring S1, which itself bears on the part -The increased size of this volume over all on the cone of the stopper. The two washers G fixed to the bottom of the valve chamber. The previous issues of this useful handbook is are coated with a mastic composed of equal parts upper part of the apparatus has a stuffing-box, noteworthy. (The increase is about 100 pages of yellow wax, pitch, and tallow. By the V, of semi-hardened caoutchouc, through which over the last edition, and 300 pages over the screwing of the stopper into the end of the passes a metal rod T fitted with a handlet for |