matter in the hands of the Academy. The following letter from Napoleon, dated from the Camp at Boulogne, 21st July, 1804, and addressed to M. de Champagny, Minister of the Interior, proves the contrary. It is given on the authority of Cosmos :

"I have just read the project of citizen Fulton, an engineer, which you sent me much too late, for it seems capable of changing the face of the world. At all events, I desire that you will immediately place the examination of it in the hands of a committee, composed of members of the Institute, for it is to them that the scientific men of Europe will naturally look for a decision on the question. A great physical truth stands revealed before my eyes. It will be for these gentlemen to see it, and endeavour to avail themselves of it. As soon as the report is made it will be sent to you, and you will forward it to me. Let the decision be given in a week, if possible, for I am impatient to hear it."

ROTARY ENGINES.

Loose or sliding

MESSRS. J. and W. COOKE, of Shrewsbury, have provisionally specified a new or improved Rotary Machine to be used as a steamengine, water-wheel, fire-engine, or pump, which consists of a drum revolving on a shaft or axis. The said drum is contained in an iron. ring, forming therewith a steam-tight circular passage. One or more pistons are fixed in the said steam passage. pistons are placed on and work in the drum in the direction of radii, and are carried round with it in its motion on its axis. Fixed combs on the sides of the steam chest or passage engage with the sliding pistons, and draw them towards the centre as they approach and pass the fixed pistons. One of the sliding or loose pistons occupies the. steam passage, while the other is being withdrawn to pass the fixed piston. The moveable pistons are carried round by the steam as it passes to the exhaust pipe, and carry round the drum and shaft to which they are connected. The machine is wholly covered by a steam-tight chest, or it may be enclosed in the boiler, excepting the exhaust pipe. Although only described as a steam-engine, it may be used as a water-wheel, fire-engine, or pump. When used as a machine for raising and forcing liquids, motion is given to the central shaft. When used with water as a motive-power engine, it is used essentially in the manner first described.—Mining Journal.

STEAM PENDULUM.

MR. E. A. BROOMAN, of Fleet-street, has patented a communicated invention, which consists in causing steam to act upon a pendulum to make it vibrate, and in communicating power to a crank through a connecting-rod affixed to the shaft of the pendulum. The pendulum is suspended from a shaft supported on bearings in a suitable frame, and has connected to it at opposite sides two pipes. At opposite ends of the frame, and near the end of the course of the pendulum, are two other fixed pipes, which are received by and enters into the pendulum pipes. Slide-valves, worked by projections upon a boss on the top of the pendulum shaft, admit steam into and cut it off from the fixed pipes. Steam being admitted into one of the fixed pipes, rushes into one of the pendulum pipes, and impels the pendulum towards the opposite fixed pipe, the steam escaping out

of the pendulum pipe into the atmosphere. On the pendulum arriving near the end of its vibration, steam is admitted into the opposite fixed pipe, checks any shock, and drives back the pendulum, the vibrations being continued by the admission of steam alternately into the fixed pipes. A governor regulates the admission of steam to the fixed pipes. This invention is susceptible of several modifications; for instance, instead of the steam escaping directly into the atmosphere, the pendulum and fixed pipes might be made so long that they should continually work one within the other, and then the pendulum on its return vibration might be made to expel the steam which had served first to drive it through a passage to be opened by one of the slide-valves.-Mining Journal.

NATURE AND EFFECTS OF DEPOSITS IN BOILERS.

As opinion is much divided upon the nature and effects of Steam Boiler Deposits, and as the subject is one of great importance, we have much pleasure in publishing the following report of an analysis made by Dr. Edwards, of Liverpool, for Mr. C. Wye Williams, to test the heat-conducting power of such deposit. This is the first instance in which we have known boiler incrustations to be formally analysed.-Mechanics' Magazine, No. 1752.

Royal Institution Laboratory, Liverpool, 26th Feb., 1857. Analysis of crystalline deposit from boilers; very hard; whitish brown colour; crystallized in repeated layers of small prisms; inner surface (in contact with the water) rough and nodular; specific gravity, 2'82, at 60° Fahr., contains

Sulphate of lime

Water of crystallizing action

Sulphate of magnesia.

78.00

14:00

3.20

1.60

2.20

1:00

100'000

The above analysis shows that the crystalline deposit consists chiefly of dihydrated sulphate of lime crystallized in prisms. The other salts appear to me to be deposited between each act of crystallization, which forms a layer of the saline constituents of the water adherent to the primary crystals of the sulphate of lime, and may thus be regarded as impurity, and of secondary importance; the definite crystallization of the gypsum would doubtless operate greatly in increasing its power as a conductor of heat.

With reference to the conducting power of this deposit, I experimented with a vessel, the bottom of which was formed of the same, half an inch thick. I found the heat passed rapidly through the material, and that the highest temperature attained by the outer surface during a continued boiling was 240° Fahr. Such a temperature cannot injure the iron boiler plates, and it seems to me that this species of incrustation is a sufficiently good conductor of heat to prevent the iron becoming injuriously heated.

A NEW BOILER.

MR. M. ATKINSON, of the Grove Boiler Works, Southwark, has designed this New Boiler principally for heating large quantities of air for warming and ventilating hospitals, churches, or other large buildings. The boiler is of the upright circular form, quite inde

pendent of brickwork, or chimney-stalk, and has no appearance of the ordinary furnace or stoking-hole about it. The fuel, coal or coke, is dropped through an aperture in the dome, into a small cockle furnace, in the centre of the apparatus, and is entirely surrounded by the water space. This water space is also surrounded, horizontally, by an annular air chamber, and this is again surrounded by another water space. These two water spaces are connected by means of a series of 2-inch iron pipes or tubes, passing through the air chamber, and radiating outwards and upwards from the central furnace, near to the surface of which the lower ends of the tubes are situated, thereby conducing to rapidity of circulation.-Builder, No. 729.

VENTILATION BY THE STEAM JET.

MR. F. H. PEARCE, of the Bowling Ironworks, near Bradford, thus applies the Steam Jet for the purpose of ventilating a coal mine, in a pumping-shaft 120 yards in depth, the ventilation of which had been stopped by the water rising at the bottom of the pit during the time some alterations were being made in the pumps. The water having stopped the air-courses, the pit, to within a few yards of the top, became full of the gas known to miners as black or choke damp, which appears to have been discharged freely from some old workings, and thus it was rendered an impossibility for the workmen to descend until the removal of the gas had been effected, and a constant current of pure air produced in the pit. Mr. Pearce has succeeded in maintaining so perfect a ventilation of the above-mentioned pit, simply by allowing a small jet of steam to issue into the atmosphere at a few feet from the top of the pipes through which the water is forced up when the pumps are at work, that the pit can be worked with perfect safety. The workmen were enabled to descend thirty minutes after the steam had been turned into the pipes. The principle is exceedingly simple. The jet of steam issuing from the top of the pipes, produces in them a partial vacuum, which draws the foul air up these pipes, and thence out of the pit, with very great velocity. The cost of supplying the steam jet in the above manner is very trifling; and this method of ventilation will doubtless be found a very safe and useful one in many instances, particularly in sinking deep shafts. In addition to other advantages, wood or any other kind of pipes may be used. It requires little or no attention, no machinery to get out of repair, produces a powerful current of air, and can be regulated at pleasure. As the steam is discharged into the atmosphere above the top of the pit, it does not interfere with the men working in the shaft.

HEAT IN AGITATED WATER.

MR. GEORGE RENNIE has communicated to the British Association his continued "Report on the Development of Heat in Agitated Water." Mr. Rennie, in alluding to his former papers on the subject, read before the Section in 1856, at Cheltenham, stated that the subject of the mechanical or dynamic force required to raise a given quantity of water one degree of Fahrenheit had long been the object

of the research of philosophers ever since Count Rumford, in his celebrated experiments on the evolution of heat in boring guns when surrounded by ice or water, proved the power required to raise one pound of water one degree, and which he valued at the dynamic equivalent of 1034 lb. M. Moya was the first who announced that heat was evolved from agitated water. The second was Mr. Joule, who announced that heat was evolved by water passing through narrow tubes, and by this method each degree of heat required for its evolution a mechanical force of 770 lb. Subsequently, in 1845 and 1847, he arrived at a dynamical equivalent of 772 lb. These experiments had since been confirmed by other philosophers on the Continent. In the present paper Mr. Rennie stated that his attention was called to the subject by observing the evolution of heat by the sea in a storm, by the heat from water running in sluices. He, therefore, prepared an apparatus similar to a patent churn, somewhat similar to that adopted by Mr. Joule, but on a large scale. In the first case he experimented on fifty gallons, or 500 lb. of water, inclosed in a cubical box, and driven by a steam-engine instead of a weight falling from a given height, as in Mr. Joule's experiment; secondly, on a smaller scale, by 10 lb. of water inclosed in a box. The large machine or churn was driven at a slow velocity of eightyeight revolutions per minute, and the smaller machine at the rate of 232 revolutions per minute, so that the heat given off by the water in the large box was only at the rate of three and a half degrees per hour, including the heat lost by radiation; whereas the heat evolved by the ten gallons of water contained in the small box agitated at 232 revolutions was fifty-six degrees Fahrenheit per hour. Thus the temperature of the water in the large box was raised from sixty degrees to 144 degrees, and the temperature of the water in the small box to boiling point. As an illustration, an egg was boiled hard in six minutes. The mechanical equivalent in the first case was found to approximate nearly to that of Mr. Joule, but in the latter case it was considerably above his equivalent, arising, very probably, from the difficulty of measuring accurately the retarding forces.

TUXFORD'S TRACTION ENGINE.

AT the Smithfield Club Show, and the Agricultural Machinery exhibited there in 1857, we noticed the Portable Steam Engine of the Messrs. Tuxford and Sons, of Boston, Lincolnshire; this being the third year this eminent firm have held the first prize of the Royal Agricultural Society of England.

The Messrs. Tuxford and Sons were the pioneers of farmers' portable engines and combined thrashing-machines, and are now engaged in developing a new feature in agricultural mechanics-the Traction Engine, or Steam Horse-a sort of walking leviathan, more powerful than the elephant, yet as manageable as the farmer's bestbred cart-horse. A number of these self-moving machines are in course of construction, or are already completed, for some extensive sugar plantations in the West Indies. Senor Placidè Gener, of Matanzas, Cuba, a large landed proprietor and sugar-planter of that

island, who holds the exclusive right for the introduction of the traction-engine into the Spanish West Indies, has been for some time in England superintending the manufacture of several of the engines, which he intends for ploughing, for drawing in cars the produce of the fields to the mill, for carrying the sugar from the mill to a railway some miles distant, and also for working as stationary engines when not otherwise employed.

In appearance, the traction-engine has a massiveness which, at first sight, leads to an inference that, from its weight, it is not adapted for travelling across grass-lands or over light soils. The reverse is the fact: the slippers or shoes, with the rails upon them, which are attached to the wheels, and over which the wheels themselves travel, offer to the surface of the land an area, with the whole weight of the engine upon them, twice as great as that presented by the feet of either horses or oxen when walking with their proportionate weight. Hence the simple downward pressure, or sinking into the soil, of the traction-engine will be only one-half of that of horses or oxen, when any of them are employed for traction purposes. This is an important fact, and must be borne in mind by every one before expressing an opinion as to the fitness or nonadaptation of so massive a machine for agricultural purposes. The very weight itself is essential for obtaining the end desired. With a heavy load behind it, and without a given weight upon the land from the engine as a resistance, the power of the engine would be expended without any forward movement.

The action of the endless railway-wheels is precisely that of walking; the slipper being the foot, its heel first touches the ground, and the toe last; the cycloidal iron at its apex forms the ankle, and the nave of the wheel the knee. The wheel, in its revolution, brings down six of these feet, to which there is but one common knee, the

centre or nave.

It is not so much to this endless railway that attention here need be directed, as the credit of its invention belongs to Mr. Boydell ; but it is to the mechanical combination by which the Messrs. Tuxford have been able to make these railway-wheels signally successful with steam-power. The difficulty hitherto experienced in making turns when travelling to either side has, in this engine, been surmounted; and the power from the two cylinders can be given off equally to each of the impelling-wheels, or a greater power given to one and a less to the other, or either of the wheels can be detached from the power instantaneously, and without the least shock or jar. This engine weighs altogether about twelve tons.-Illustrated London News, No. 893.

ROMAINE'S STEAM CULTIVATOR.

A TRIAL of this machine, the invention of Mr. Robert Romaine, a Canadian, took place lately in a field near Crosskill's Agricultural Implement Works, Beverley, where the Cultivator had been constructed. It differs from all others hitherto brought before the public for the purpose of applying steam power to the cultivation of the soil, in entirely dispensing with the use of ploughs, ropes, or auxiliary

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