strength in the parts which attach the breech to the barrel; a slight accident might bend or otherwise derange the screw bolts which connect the stock to the barrel, which, if it did not render the piece useless, would throw the breech and barrel out of line, a very grave objection on all accounts.

It is also evident that the junction of the barrel and breech, these parts being merely in contact by the bending down of the breech, must leave some space for the escape of vapor during the discharge, which will increase by wear, during use. It is probable that the ingredients of the powder may produce irregular corrosive action on the surfaces of junction, which could not be compensated by the screw bolts, from which a loss of propulsive power would result.

There is some doubt as to the strength of the ties between the barrel and stock; an accident from failure in this respect would be disas trous. The utmost caution, therefore should be exercised to guard against the possibility of its occurrence.

These views are necessarily speculative, and must be received as the opinions of the committee, after examination and reflection, for whatever they are worth. A faithful trial, by oft repeated discharges under ordinary circumstances, such as could be given by the ordnance department of the General Government, would either establish its merits, or consign it to its just fate.

The committee have expressed no opinion as to the originality of the above improvement; not having investigated that point. By order of the Committee,

Philadelphia, Sept. 11, 1845.

WILLIAM HAMILTON, Actuary.

MECHANICS, PHYSICS, AND CHEMISTRY.

TO THE COMMITTEE ON PUBLICATION OF THE JOURNAL OF THE FRANKLIN INSTITUTE.

Albany, Nov. 3, 1845.

GENTLEMEN,-We have lately attached to a cupola furnace for melting iron an apparatus for heating the blast, the operation of which has produced great economy in the consumption of coal. Designing that the public should not remain uninformed of so great an improvement, and believing that it excels in its economical operation all other cupolas, I take the liberty of enclosing to you, for publication in the "Journal of the Franklin Institute," a description of the same.

Improved Cupola for Melting Iron, constructed by MESSRS. FRANKLIN TOWNSEND, & Co., Albany, N. Y.

This cupola is of the ordinary construction, only being of enlarged dimensions, and made of cast iron. Its diameter at the tuyères, when lined with fire brick, is three feet; and its height, from the hearth to

the charging door, eleven feet. When charged full, it will contain three tons of pig iron, and is capable of melting upwards of twelve tons at one blast. The air is admitted into the cupola by six tuyères, which are placed about fifteen inches above the hearth, and equidistant on the circumference of the cylinder. To avoid the number of pipes which would be necessary if the air were conducted into the cupola by the usual method, an air chamber is made to surround the cylinder and enclose all the tuyères, and into this the main blast pipe is introduced. An opening is made through the outside of this air chamber, and directly opposite to each tuyère, which, being protected by a plate of glass, allows the melter to observe the working of the furnace. This plate of glass is so attached that it can be easily removed, and thus give free entrance to clear the tuyères whenever it may be necessary.

For

The air is heated by being forced through a number of small pipes, placed in such a manner in the interior of the stalk immediately above and directly over the cylinder of the cupola, that their outside surfaces are exposed to the full action of the waste heat of the furnace. reason of the difficulty caused by the expansion of the metal when heated, these pipes are required to be of peculiar construction. By this arrangement, the air becomes heated during its passage from the blast resorvoir to the tuyères, upwards of 400° Fahrenheit's ther

mometer.

This cupola has been in operation during the past three months, melting ten tons of iron daily. The iron is charged in the shape of pig and scrap (sprues, gates, &c.) in about equal proportions, and is cast into stove-plates, which requires that it should be very hot and liquid. The average consumption of coal (Lehigh) in melting this quantity of iron, is 225 lbs. to the ton of iron, and the rate of melting is from two to three tons per hour. An ordinary cupola, operated with cold blast, consumes upwards of 500 lbs. of coal to the ton of iron, and its rate of melting is from one to two tons per hour.

Not having the results of the operation of any hot blast cupola in this country, the comparison of the working of this improved cupola with them cannot be given; but its evident superiority to those of England is shown by the following extracts from a report* made by M. Dufresnoy, chief engineer of mines.

"The cupola furnaces at the Tyne Iron Works' are operated with heated air. The consumption of coke is 280 livres (309 lbs.) to the ton of iron; rate of melting, one ton per hour.

"At Wednesbury, the cupolas are operated with hot blast, and consume 260 livres (287 lbs.) of coke to the ton of iron. Before the adoption of the hot blast, the consumption of coke was 400 livres (441 lbs.) to the ton of iron. The same quantity of iron is melted in onehalf of the time that was required before the adoption of this pro

cess."

*Extrait d'un rapport de M. Dufresnoy, ingénieur en chef des mines, sur l'emploi de l'air chaud dans les usines à fer de l'Ecosse et de l'Angleterre.-Bulletin de la Société d'Encouragement pour l' Industrie Nationale.-1834, p. 299. See also Journal Franklin Institute, vol. xv, 2nd series, for the whole of M. Dufresnoy's report.

The Globes Celestial and Terrestrial. By A. DE MORGAN.

This treatise is written to accompany Malby & Son's new globes and planispheres. The Messrs. Malby are spirited publishers of globes, as their prospectuses show; and reasonable ones too, in the delightful modern English sense of the word. Among the novelties they have put forward, is a globe which they call perennial, meaning that it can give the procession of the equinoxes, and thus enable any one to verify the astronomy of Hesiod or Eudoxes, without calculation. One of the last astronomical labors of Mr. Baily was the drawing a set of boundaries for Malby's celestial globes, so as to remove a few of the glaring anomalies which are usually presented. The new boundaries are in a broad line; the old ones, where the two differ, in a thin line. As to the treatise, the points in which it differs from others are briefly these-Only the appearances of astronomy are explained, on the ground that the globe is connected with them alone: two persons, one of whom follows Ptolemy, and the other Copernicus, meet on common ground when they use a globe. Mr. De Morgan is of opinion that the general ignorance of the actual phenomena of the heavens makes it desirable that books on globes should confine themselves to appearances, and leave explanations of the appearances, and the grounds of them, to books on astronomy. Next, the tables of Ferguson for finding the new and full moon are given in an appendix, so that any person who is an adept (we had almost written add-ept,) at common addition can find his new or full moon for any month of any year from B. c. 1000 to A. D. 2000 within about a quarter of an hour. This introduces the beginner to an idea of astronomical tables: for the manner in which the moon's place is found from day to day in the Nautical Almanac is only by a larger quantity of the same sort of work.

British Woolen Manufactures and Wool.

Returns upon this subject were issued on Saturday, by order of the House of Commons (on motions of Mr. Masterman and Mr. Aldam.) It thence appears that the declared value of the British woolen manufactures exported from the United Kingdom in 1844 was £8,204,836, of which £2,444,789-worth was exported to the United States of America. During the same year 65,079,524 lbs of sheep and lambs' wool, foreign and colonial, were imported into the United Kingdom, of which 1,924,826 lbs. were re-exported from the United Kingdom, chiefly to Belgium. Of British sheep and lambs' wool, 8,947,619 lbs. were exported to foreign countries; and 8,271,906 lbs. of British woolen and worsted yarn, including yarn of wool or worsted mixed with other materials. There were also imported into the United Kingdom 635,357 lbs. (of which 47,848 lbs. were re-exported) of alpaca and llama wool; and 1,290,771 lbs. of mohair, or goats' wool, of which 97,529 lbs. were re-exported. London Farmer's Mag.

On the Registry of the Hourly Variations of the Thermometer by means of Photographic Papers. By MUNGO PONTON, ESQ. F. R. S. E., F. R. S. S. A. Read before the Royal Scottish Society of Arts, 10th March, 1845.

An unexceptionable mode of registering the hourly variations of the common mercurial thermometer, has long been a desideratum in science. Hitherto we have been able to register only the maximum and minimum of temperature for each day and night, and even that in rather an imperfect manner; but to record the hourly movements of the mercury in the thermometer has not, so far as I am aware, been as yet successfully attempted. Various purely mechanical methods have been tried from time to time, but without satisfactory results. Nature, however, is full of appliances; and it only requires perseverance on our part to avail ourselves of the implements so profusely scattered around us.

The newly discovered phenomena of photography appeared to ine likely to afford facilities for attaining the object in view; and the results I have arrived at lead me to hope, that we may successfully employ light to record, with its subtile pencil, the changes in the heat of the atmosphere.

The first difficulty to be overcome was to obtain a clear and well defined shadow of the filled portion of the bore of the thermometer, capable of being distinguished from the shadow produced by the empty portion. This is a matter of some nicety. After several trials, the following appeared to be the best mode of securing this result: Select a thermometer with a flat bore, and grind the stem down on one side nearly to the bore, so as to produce a flat, or rather slightly concave polished surface, and let the opposite side be ground only a little flat. If the latter flattened side be now exposed to the light of a lamp or gas flame, condensed by means of a cylindrical glass vessel filled with water, placed at a considerable angle, it will be found, that by a little nice adjustment, a certain position will be obtained, in which the shadow of the bore may be thrown on a piece of paper placed against the other ground surface of the stem, in such a manner that the shadow of the empty part of the bore is reduced almost to nothing, while that of the filled portion is considerably expanded and well defined. A little practice suffices to hit the best adjustment.

The next point was to obtain a photographic paper sufficiently sensitive to be affected by artificial light at a convenient distance, and in a sufficiently short time, but which could at the same time be kept long enough without injury. After various unsuccessful attempts, I have ascertained that paper prepared in the manner to be described, answers the purpose perfectly. The process is a modification of that discovered by Hunt, and to which he has given the name of Energiatype.

The paper is first to be coated with either the iodide or the chloride of silver; I prefer the latter. The usual mode of washing, first with the nitrate of silver, and then with either the iodide of potassium, or VOL. X, 3RD SERIES.-No. 6.-DECEMBER, 1845.

35

the chloride of sodium, may be adopted for this purpose. It is desirable to have a good coating of either the iodide or chloride of silver on the paper. The soluble salt having been well washed out, by immersing the paper in clean cold water, it is next to have applied to it a saturated solution of succinic acid. In this state the paper may be preserved for any length of time, if kept dry, and carefully excluded from light.

Before use, a wash of the aceto-nitrate of silver, as directed to be prepared by Talbot, is to be applied. This gives the paper the necessary degree of sensitiveness, and in this state it may be kept without injury to its properties for two or three days, but not more.

If the aceto-nitrate be applied without the previous wash of succinic acid, the paper will be equally sensitive; but it will blacken. spontaneously in the dark, and is therefore useless for the purpose. The succinic acid thus appears to exert a conservative influence in preventing spontaneous decomposition.

The photographic image formed on this paper is latent, and requires to be brought out by the application of a saturated solution of the sulphate of iron, mixed with three or four times its bulk of mucilage of gum-arabic. This mixture should be freshly prepared, for it soon becomes a jelly, which is unfit for use. The application of the sulphate of iron to the paper may be made at the distance of upwards of 24 hours from the time of the first impression of the latent image, which will, notwithstanding that lapse of time, come out distinctly; and thus a whole day's record may be brought out at once. The aid of a little heat is sometimes necessary for the development of the image.

The mechanical arrangements are these:-A black japanned cylinder of tin, about 4 inches diameter, and 44 inches deep, has a piece of the sensitive paper wrapped round it. This cylinder is intended to be moved round by a time-piece, and to traverse behind the stem of the thermometer. It will be stationary for a half or a quarter of an hour as desired, at each division of the cylinder, and then be moved a division by a jerk. There will thus be time for the image to be completely formed by the action of the light. Around the cylinder carrying the sensitive paper is another blackened cylinder, 44 inches diameter and 4 inches deep, with a slit in it just sufficient to admit the stem of the thermometer. This is intended to screen from the light all that portion of the paper which is not in action. A cover goes over the whole, the more effectually to exclude all light except that which passes through the stem of the thermometer. The stem itself is also furnished with wings of black paper, to prevent the light from spreading on either side.

The thermometer should have its stem twice the length of what is required for the natural range of temperature, so that the bulb may be placed at a considerable distance from the portion acted on by the ight, in case of any increase of temperature from that cause; and the bulb and lower portion of the stem should be completely screened from the light. This is accomplished by placing the thermometer in a wooden box, the bulb and the lower half of the stem being in the