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this arrangement to the notice of cabinet makers, and induce us to give it our approbation.

We must, however, recommend, that a wrench with a square end, adapted to the management of this contrivance, should in all cases be furnished by the maker, with bedsteads so constructed.

By order of the Committee,

Philadelphia, January 9th, 1845.

WM. HAMILTON, Actuary.

Savery & Co.'s Enameled Cast Iron Ware.

The Commitee on Science and the Arts constituted by the Franklin Institute of the State of Pennsylvania, for the promotion of the Mechanic Arts, to whom was referred for exami. nation specimens of Enameled Cast Iron Ware, manufactured by Messrs. Savery & Co., of Philadelphia, Penna., REPORT:

That, they have examined the ware, both by inspection and by mechanical and chemical experiment. The two articles more minutely examined were a griddle, or baking-iron, and a small pot for boiling liquids. The mixture composing the enamel consists, probably, of silex, clay, flint glass and borax; and the two articles seem to have been differently coated, for they withstand chemical and mechanical action differently. The enamel on the griddle is superior to that of the pot, and was severely tested, by placing it directly on a hot fire and throwing water on it, which had no effect in loosening or cracking the enamel. On breaking the enamel, subsequently, with a hammer, but a small particle was removed at each blow, and even after the subjacent surface of iron had been exposed, the hammer still continued to remove only small fragments. The enamel, therefore, possesses considerable toughness, is very hard, and adheres with great firmness to the surface of the metal. Nor could openings or pores be detected in it which extended to the metal, and might loosen the adhesion after continued use and cause the enamel to scale off. The surface of this enamel was as smooth as is desirable for the purposes for which it is designed, and it possessed a sufficient degree of white

ness.

The glazing of the pot was more rough on the surface, less white, covered with numerous small black specks, or spots, and a number of small holes or pores were detected, into which a pin might be thrust to the subjacent iron. Muriatic acid heated in the pot for 15 minutes dissolved but little iron, although when nitric was added to it, a large proportion of iron was dissolved, in the cold, in 24 hours. A portion of the iron dissolved was, probably, due to the black specks above mentioned, for after removing the acid, the surface was much more free from them, but a portion was also due to iron dissolved out through the small pores. For by putting the acid in one part, where a single pore was observed, and letting it remain for a few days, the glazing scaled off readily around the pore. It should be observed, that the glazing could be picked off piece-wise, by a knife, when the pot was first examined, previous to the chemical tests.

Additional experiments, with a larger enameled iron pot, proved its glazing to be of fair quality, having the desirable physical qualities of hardness, toughness and whiteness, and offering sufficient resistance to acids. It still presented the defect of pores, observable in the smaller pot.

In the opinion of the Committee, if the griddle alone should be considered as an example of the ware, it is of superior quality, being white, smooth, hard, tough, adhering with great force to the iron, and presenting great resistance to chemical agents. If the smaller pot be the standard, the ware is not perfected. If we draw conclusions from both specimens, it is that the manufacturers are capable of producing an article of the best quality, but that the products of their manufacture are not always uniform. If the ware could always be made of the same quality with the griddle, it would deserve high commendation.

The presence of flint-glass in the composition is decidedly objectionable, for its content of oxide of lead will be a constant cause of a darkening or blackening of the surface when some liquids are introduced into an enameled vessel and heated in it. It will, therefore, be the manufacturer's interest to substitute a leadless glass for flint-glass, which is successfully done in England and on the continent of Europe. But the presence of lead is objectionable on a higher ground, viz: its injurious effects when introduced into food, which may readily take place, especially where much alkaline matter is present in the enamel. Now, although a small quantity of lead in the glazing might not be injurious, yet it would be easy to introduce a larger quantity; a temptation to which the manufacturer is exposed from its greater economy and fluxing power. It is therefore advisable to reject its use altogether.

The use of borax presents the advantage of cleansing the surface of iron more or less during the fusion of the glaze, and causes the whole body of the glazing to adhere more firmly to the metal; but the previous cleansing of the surface of metal by acid or acid salts should not be dispensed with.

By a careful selection of pure quartz and kaolin, which may be termed the body of the glaze, and by a careful fusion of the materials, the glaze may be obtained perfectly white, and free from the black spots alluded to in the above ware.

Lastly, by the successive applications of a finely powdered glaze, that is, by two successive fusions, its surface will be rendered more smooth and beautiful in appearance, and less liable to the formation of pores. By order of the Committee,

Philadelphia, April 10th, 1845.

WM. HAMILTON, Actuary.

A Mode of Tanning Leather by means of a Flagellator. The Committee on Science and the Arts constituted by the Franklin Institute of the State of Pennsylvania, for the promotion of the Mechanic Arts, to whom was referred for exami. nation a mode of Tanning Leather by means of a Flagellator, patented in June, 1844, by Robert Downey, New Albany, Floyd County, Indiana, REPORT:—

That the object of the invention is to diminish the length of time

required in tanning, an object which has been kept in view of tanners during the last half century of general improvement in the arts, as witnessed by the almost numberless patents issued in various parts of Europe and the United States, during the time specified. These attempts have been successful to a very limited extent, since the general experience has been that in proportion as the time is diminished, the quality of the tanned leather is injured, or, up to a certain point, the quality is inversely as the time employed in tanning. Nevertheless, at the present time, it would be wrong to assert that a more rapid process, compatible with quality, cannot be devised.

Mr. Downey proposes flagellation, as the means of diminishing the time, on the assumed principle that the pores of the hide are closed in the ordinary tanning process, preventing thereby the entrance of the bark liquor. By flagellation with a machine, he believes that the hide is raised and thickened, the pores opened, and while the gelatin and gluten are oozing out, the bark liquor is driven in.

Without farther noticing the mistake in confounding gelatin and gluten, we observe two principles assumed; 1, "the closing of the pores by bark or its infusion;" 2, "the oozing out of gelatin."

1. The committee cannot agree with the proposition that the pores of the hide are closed, certainly not closed in such a manner as to prevent the solution of tannin from entering into them, and they confidently believe that all experience shows that the pores are open and remain so; for the length of time required in the ordinary process cannot possibly be ascribed to the extreme slowness of infiltration through closed pores. Where hides are suffered to remain too long in the handler, or on a layer, especially during the warm season, without renewing the supply of fresh bark, a species of fermentation produces a mucilaginous or slimy coating, which closes the pores more or less effectually, and this may be viewed as the only case in which a closing of the pores takes place.

2. The oozing out of gelatin" is erroneous; for the practical tanner knows of no case of the loss of gelatin by mechanical means, and it may be shown to be impossible on chemical grounds. The gelatin does not exist ready formed in the hide, but by the action of hot water the tissues are transformed into gelatin, and the same takes place slowly during the operation of tanning, lapse of time with the conjoint action of tannin in solution performing the transformation which heat effects rapidly. But, on the other hand, admitting the proposition to be true that flagellation presses out gelatin, the tanner can show that it would be positively injurious; for the leather would not exhibit that increase in weight which it is his aim to produce, not merely for the increased profits due to the greater number of pounds, but because this increase in weight increases the firmness and durability of the leather. Gelatin combines with a certain proportional quantity of tannin constituting leather; hence, when a portion of the former is lost, there is nothing to replace it, for the remaining gelatin will only take up its due proportion of tannin and no more, and all other matter added to restore the lost weight would be mechanically

intermingled or lodged in the leather, while nothing can compensate for the loss of firmness and durability.

The committee would state that no samples of leather having been offered them prepared by Downey's process, they have judged of the value of the process on general principles.

By order of the Committee,

Philadelphia, April 10th, 1845.

WM. HAMILTON, Actuary.

MECHANICS, PHYSICS, AND CHEMISTRY.

The Progress and Present State of the Daguerreotype Art. By M. CLAUDET.

The discovery of a new art founded upon some startling facts in science, however perfect it may appear at the beginning, and little subject to improvement, rarely remains long stationary; and still more rarely can we foresee all its useful applications.

As this observation applies particularly to the ingenious and curious discovery of Daguerre, it may be interesting at the present moment to examine the progress it has made during the last four years, and to determine its present state, in order that we may be able to compare, at given periods, the various stages of improvement through which photography has passed.

The daguerreotype has opened two extensive fields of inquiry: the one, for the investigation of facts, by which the sciences are to enrich themselves, and by which some of the phenomena of the laws of nature may be explained; the other, for the advantage of society, in reference to the creation of a new branch of manufacture, and to a new art, which are destined to give employment to many persous; to which may be added the improvements that the daguerreotype will introduce in the fine arts.

It has been remarked that the discovery of photography was as great a step in the fine arts as that of the steam engine in the mechanical arts. There is no exaggeration in this observation; and certainly our age (which is the era, not of wars and conquests, but of social improvements, of emulation in the arts, sciences, and manufactures,) will be celebrated in future times for this extraordinary invention.

It is curious to observe how rapidly sometimes new discoveries are followed by other important discoveries, forming the links of a mysterious and infinite chain, one end of which approaches the great Creator of all things.

In the year 1811, Courtois discovered the chemical substance called Iodine, and, as late as 1826, Balard discovered Bromine; these two elements are the only substances which, in the daguerreotype, form with the silver a compound sufficiently sensitive to the rays of light, and without which substances the daguerreotype could not have existed.

Such is the progress of science, that there is no fact, however insignificant it may appear at first, which does not aid the advancement of philosophy, and the improvement of mankind.

When these new elements were first discovered, how little was it thought that they would so soon become the source of the magic invention of the daguerreotype, which again will undoubtedly lead to other discoveries, perhaps far more important than itself!

There are some persons who, although admiring the daguerreotype in its effects, perceive nothing beyond the mere spontaneous, although beautiful reproduction of objects-the representation of a building or a landscape in their minutest detail, and in the portraying of human features: but this is only the useful and immediate application of the art in its state of infancy; its destinies are of a much higher order.

It may be said that already optical science has been much benefitted by it. Never before has it been found so necessary to construct object glasses with the shortest possible focus, without increasing their aberration; this has now been done, and we have double achromatic object-glasses refracting a perfectly well-defined image upon a screen of seven inches in diameter, although the focal length is not more than eight or nine inches: this improvement in the object-glasses of the camera obscura, being also applicable to the construction of telescopes, will enable opticians to make powerful instruments of a considerably smaller bulk.

The science of optics, the study of which was confided almost exclusively to professional opticians and astronomers, is now in the hands of a thousand operators in photography, who are constantly studying and endeavouring to correct the imperfections of their apparatus; and their researches and investigations will, no doubt, ultimately lead to many useful discoveries.

In passing from the practical part of optics to that which is purely theoretical, that which treats of the various rays emanating from the sun, of their laws and properties, and of the principles and phenomena of light, considered as a whole, or a compound of various kinds of matter (if I may be allowed the expression,) as being produced by emission or by undulation; if these interesting points are ever better explained and understood than they are at present, it appears highly probable that the daguerreotype will be the instrument leading to these results: at least it is certain that, in experiments and researches upon this subject, philosophers will be greatly assisted by the innumerable facts collected in the daguerreotype operation.

The existence of invisible or chemical rays is proved by the various processes of photography; for in speaking of the daguerreotype, we cannot omit to mention the beautiful discovery of Mr. Talbot, which he has called the Calotype. Neither must we omit the curious discoveries of Sir John Herschel, forming another step in photography, which is called by that learned astronomer Crysotype.

The experiments made in these various photographic processes all agree in the fact, that the rays which produce a change upon the sensitive screen are not the rays of light, but other rays traveling with light, and emanating from the same source, which are sometimes more

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