public. The advantages claimed for Mr. Todd's apparatus are portability, the little attendance required, and the small weekly cost of keeping up the required temperature. The whole contrivance is enclosed in a vessel of cylindrical form, made of sheet iron, whose diameter is 24 inches, and height 22 inches. It consists of the following parts:-The hatching tray, occupying the upper part of the vessel, which is 21 inches in diameter and 22 inches deep, is lined with wool, and has around a central aperture, through which the steam passes from the boiler to the hatching department, a reservoir of annular form, 11⁄2 inches wide and 14 inches deep, to contain water for the purpose of keeping the atmosphere of the hatching compartment in a sufficiently humid state. The boiler, of zinc, is placed 34 inches below the bottom of the hatching tray, is 22 inches in diameter, and 10 inches in extreme depth, the upper and lower sides being of a somewhat hemispherical form. The boiler is filled with hot water by a inch pipe, passing out on one side of the vessel into a vertical reservoir of 2 inches diameter and 5 inches high. In the centre of this reservoir is a cylindrical case, in which a thin copper wire, suspended from a float in the upper part of the reservoir, works freely, and which is connected with a valve at bottom, working in a small pipe communicating with the heating chamber. The use of the float and valve is to regulate the temperature of the water. The heating chamber is of copper, about 4 inches square, and 19 inches long, running in a central line through the boiler. It is furnished with a lamp tray having any number of burners that may be required, according to the temperature of the apartment in which the apparatus is placed. The lamp tray, in the present case, is 7 inches long, 4 in width, and 1 in depth. The hatching process is simple, and may be thus described :— When the eggs are first placed in the hatching tray, it is necessary to mark 1 and 2, or A and B, or some other mark, by which to distinguish opposite sides; as also to write the date on each egg, so as to distinguish one batch of eggs from another. The tray will hold 100 eggs. Once in every 24 hours, for 21 successive days, it is necessary (for so Nature dictates) to turn the eggs at the expiration of that time, when the chickens break forth from their shells, it is found advisable to leave them in the tray for about 24 hours, before they are transferred to the rearing compartment, the temperature of which is about 12° lower than that of the hatching room.-Proceedings of the Society of Arts; Athenæum, No. 800.

THE MONOCHORD.

ON January 18, Mr. Higgs described to the Society of Arts an instrument called the Monochord, calculated to facilitate the study of vocal music. The Monochord is an oblong rectangular box, made of mahogany, 26 inches long, 24 inches wide, and 23 inches high. On the upper surfaces are marked the diatonic and chromatic scales: a single wire is extended lengthwise over a bridge at either end of the instrument, and the different notes are produced by moving a third

bridge along the top of the instrument with the right hand, while the wire is touched with one finger of the left hand. Unlike the tuning fork, which is capable of producing only one tone or note, the Monochord produces any of the notes, either of the diatonic or any other scale. It also gives a correct idea of vibration and the theory of sound.

METALLIC SAND.

ON Nov. 29, was read to the Society of Arts, a paper by Mr. H. K. Dyer, on the Metallic Sand. This sand is produced by grinding copper slag by means of powerful machinery, and consists of iron, zinc, arsenic, and silica, the iron predominating; the slag is procured in abundance in Swansea. In chemical analysis, it is very similar to the pozzolano, and in point of durability is found to be equal to the latter. With blue lias lime, which is used for hydraulic works, the metallic sand readily enters into combination; and these having been used together for external works, exposed to all the changes of the atmosphere, have proved the indurating qualities of the Metallic Sand, after an experience of eight years. Specimens were laid on the table-1st. Brickwork of a fresh-water tank, which had been erected six years, was removed by a pickaxe, the bricks yielding to the strokes of the axe, but the cement remaining solid; 2d, imitations of marble executed by a painter on the face of stuccoed work, formed of metallic cement, in conjunction with common chalk, lime, and putty, and afterwards polished; 3d, a specimen of fresco painting, also executed on a face similar to the above; 4th, a vase, the figures on which retain their original sharpness, although it has been exposed to the amosphere for many years.

FLOOD-GATES FOR BRIDGES.

ON October 16, a communication was received by the Academy of Sciences, at Paris, from M. Fourneyron, relative to the application of Flood-gates to one of the bridges of Paris. A committee of the municipal council of Paris, of which M. Arago was president, was formed a long time ago, for the purpose of discussing the practicability of a plan for closing the arches of the Pont Neuf, or the bridge of Nôtre Dame, with gates, by which the current of the river could be regulated at will; and which, by raising the level at a certain part, would give a fall of sufficient force to work powerful turbines for the supply of water to all parts of Paris. In 1841, M. Fourneyron submitted a plan of gates of such construction that they could be worked with ease by one man; but as it was impossible to pronounce fairly on the merits of his invention without absolute experiments, the Academy and the committee of the city of Paris resolved to suspend the expression of opinion until experiments could be made. M. Fourneyron announces that for more than two months past one of his gates had been in use at Gisors, and that it had proved successful.—Athenæum, No. 835.

SELF-ACTING VENTILATOR.

MR. THOMAS WROUGHTON has invented a Self-acting Ventilator for hospitals, public schools, theatres, and other places of public resort. It consists of a ventilator connected with a mercurial valve, which is acted upon by heat; and by means of a float acting upon a sort of slide, a spring opens the ventilator, so as to admit precisely such a quantity of external air as will purify the internal atmosphere, and bring it down to a determined point. We will suppose, for instance, that it is desired that the temperature should be a fixed one of 60 degrees of Fahrenheit. The thermometer connected with his mercurial valve is fixed at sixty. As soon as the heat of the place, from the breathing of the persons assembled, or from any other cause, has raised the temperature beyond this point, the valve opens of itself, and admits as much pure air as will cool the temperature to the point desired, whilst the heated and foul air escapes.

BUILDING TIMBER.

ON Nov. 20, a paper was read to the Institute of British Archi tects, by Mr. Bailey, the Honorary Secretary, "On the several species of Foreign Fir Timber and Deals supplied to the English Market, and their respective qualities for the purposes of Building." The professed object of the paper was to present to the members, in a condensed form, the more important portions of the information relative to the growth and manufacture of the timber of the North of Europe, and of our American colonies, derived from the evidence of practical men, given before the Parliamentary Committees on the timber duties, at different times and other sources; which might be useful in assisting the judgment of the young architect, in selecting from the several kinds of timber to be found in the market, the sorts most suitable for the various purposes to which wood is applied in buildings, either for roofs, floors, framing, the external portions, and internal finishings and fittings. The relative properties, as to strength, durability, facility of working, and economy in conversion of the Memel, Dantzig, Riga, St. Petersburg, and the several descriptions of Norwegian and Swedish timber and deals, were described, and their defects noticed; as likewise those of the red and yellow pine of Canada, the use of which is daily increasing in this country. The alleged tendency of the American timber to imbibe and communicate the dry-rot was noticed, and accounted for from the treatment to which that timber is usually subjected. The larger portion of the timber and deals from Canada is floated down the river St. Lawrence to the port of shipment on rafts, becoming in consequence saturated with water, and in that condition most commonly placed in the confined hold of the ship which is to convey it to this country; the result is, that by far the larger portion, both of the timber in log, as well as the deals, on their arrival here, exhibit symptoms of the dry-rot; and if means be not adopted to repress it, the timber becomes strongly infected, and, when placed in a building, not only

rapidly decays, but communicates the rot to the timber in contact with it. If it were not for the circumstances above noticed, there is no reason to suppose that the fir timber of Canada is of a less durable nature, or inferior in quality to the European timber of the same description.

In the discussion which followed the reading of the paper, it was stated that impure pyroligneous acid still retaining the creosote had been employed with success on timbers affected with the dry rot.— Athenæum, No. 839.

A PORTABLE LIGHT-HOUSE.

An invention has been made for showing the position of a ship in danger, and thus directing the movements of persons attempting to give assistance from the shore. It consists of a composition, which, when ignited, gives a very distinct and brilliant light, and has been tried, it is said, with success at the Goldstone, where the Pegasus was wrecked.-Athenæum, No. 831.

DAY'S WINDGUARD.

MR. DAY has submitted an invention for preventing that greatest of nuisances—a smoky chimney. It consists of a cap to be placed on the top of the chimney, in which the openings whereby the smoke passes are guarded by plates of metal, in such a way that the smoke, instead of being driven by the wind down into the chimney, is blown out at the sides of these projecting plates. The contrivance seems to promise success; and its appearance is certainly an improvement on the variety of ugly fabrications for the prevention of smoke, which decorate the chimney-tops of our houses.-Athenæum, No. 831.

DEATH FROM STOVES.

In all cases of Death from Stoves, Leblanc has found there was more or less carbonic acid in the air. He has observed even one per cent. of this gas to destroy an animal in two minutes—a fact which explains many of the circumstances which appeared some years ago in the evidence of some London chemists, respecting the influence of Joyce's stoves. It is quite obvious that their structure was dangerous. Leblanc found that a candle was extinguished in air containing only from 4 to 6 per cent. of carbonic acid. In such an atmosphere, life may be kept up for some time, but respiration is oppressive. Even 3 per cent. in the atmosphere killed birds; and yet we have seen statements which affirmed that upwards of 3 per cent. had been detected in the London theatres.-Transactions of the Glasgow Philosophical Society.

109

Natural Philosophy.

THE ORDNANCE SURVEY.

Ir is with no small satisfaction that we announce to our astronomical friends the appearance of a new volume of the Trigonometrical Survey. During the long interval of thirty-one years which has elapsed since the publication of the last volume in 1811, the sole fruits of this important and costly operation have been a series of county maps-admirably executed, we admit, and of the highest value in reference to the topography of the country-still in course of preparation and publication. No observations or results connected with geodesy have been officially communicated; and, indeed, if we except the few meagre accounts which have been occasionally furnished to parliament, the public, generally, has had no information respecting the state and progress of the work. The appearance of the present volume is therefore highly gratifying, not only on account of the observations it contains, but also by reason of the promise held out that the mass of valuable results which has so long been accumulating will, at length, be available for the better determination of the dimensions and figure of the earth. After all, it may ultimately be found that the delay which has taken place in completing the meridional arc is not greatly to be regretted. Within the last twenty years, the theory of computing geodetical observations has received considerable improvements in the hands of Gauss and Bessel; and advantage will, no doubt, be taken of the new methods to render the results as perfect as possible. The instruments which have been used in the Ordnance Survey, both for the astronomical and geodetical observations, have been far superior to those which were employed in the celebrated operation for determining the French arc of meridian, and, indeed, in any of the continental surveys; and it is very important that none of the advantages of this superiority be lost through the use of imperfect, or rather, not the most perfect, methods of reduction and computation.

The contents of the present volume are sufficiently indicated by its title*. They include all the observations for purposes connected with the survey made with Ramsden's zenith sector, the chef d'œuvre of that celebrated artist. The number of stations at which observations were made is ten: namely, Dunnose, Dunkirk, Greenwich (two series), Arbury Hill, Delamere, Clifton Beacon, Burleigh Moor, Kellie Law in Fifeshire, Cowhy the Hill in Banffshire, and Balta, the easternmost of the Shetland Islands. Those at Dunnose, Greenwich (first series), Arbury Hill, and Clifton Beacon, were made in 1802, and partly published in Mudge's "Account of the Measurement of an Arc of the Meridian extending from Dunnose (in the Isle of Wight) to Clifton (in Yorkshire)," printed in the Philosophical Transactions for 1803, and in the second volume of the Trigonometrical Survey in 1804.

* Astronomical Observations made with Ramsden's Zenith Sector, together with a Catalogue of the Stars which have been observed, and the Amplitude of the Celestial Arcs deduced from the Observations at the different Stations. By Order of the Board of Ordnance.