The Complete Works of Edgar Allan Poe - Edgar Allan Poe [823]
In America, we have by no means been idle. It has been here ascertained that instead of the costly combination of glasses employed by M. Daguerre, a single Meniscus glass produces an exact and brilliant result. We have also found that we can do without the dilute nitric acid in photogeny, as well as in lithography. The process is thus greatly simplified; for the use of the acid has heretofore been considered one of the nicest points in the preparation of the plate. When unequally applied, the golden color is not uniform. Now, it is only necessary to finish the polish of the plate with dry rotten stone, well levigated and washed, using dry cotton to rub it with afterwards. We made the iodine-box, too, much shallower than does M. Daguerre. With is box, from fifteen to thirty minutes exposure of the plate was required before the proper color was produced. Four inches will be deep enough; and there should be a tray, an inch deep, fitting into the bottom of the box. Upon this tray the iodine is to be spread, and then covered with a double thickness of fine gauze, tacked to the upper edge of the tray — supports being fastened in each corner of the box, at such height as will admit of the plate being lowered to within an inch of the gauze.
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ELECTRICAL COPYING. — The new process of copying metals and other works of art on copper, by means of voltaic electricity is an invention of interest and importance. In the manufacture of plated articles and other ornaments, it is often desirable to copy ornamental work, such as leaves, flowers and arabesque mouldings, and the ordinary process is very difficult, and therefore very expensive. Mr. Spencer's late invention affords a cheap and easy method of performing what is required. By its means the rich ornaments on antique plate, or any similar work, may be copied with entire accuracy — a perfect fac-simile being taken in copper, which may then be silvered or gilt. In the art of button-making the voltaic action is used with advantage; a cast from any pattern of button may now be readily moulded in a few hours, and with little labor. Button-makers formerly required two or three sets of a particular pattern to complete one of which the die was wanting. — The whole application of the voltaic action is excessively simple and certain — the necessary apparatus may be procured for sixpence.
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MARBLE LETHOIDE. — In St. Petersburg, a method has been discovered of giving to the softest stone the hardness, and color, and consequently the polish of marble. The invention is regarded as of high importance, and of certain application. The whole details have not yet reached us — but the process appears to be analogous to that of the scagliola manufacture. The prepared substance is termed marble Lethoide.
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PNEUMATIC ENGINE. — Mr. Levi Bissell, of Newark, N. H., is said to have perfected a pneumatic apparatus, by means of which to employ the atmospheric air as a motive power. This design, in its general terms, is by no means new, an its reduction to practice has been found expensive. Mr. B.'s seems to be the old project — that of constructing pumps at convenient distances on a rail-road of air-pipe, which latter is to be exhausted of air. What is said in the papers about condensed atmosphere, with portable condensers, is probably a misunderstanding.
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RED RAIN. — In Gassendi's "Life of Peiresc," the phenomenon of red-rain which has so often excited the wonder of the ignorant, and the attention of the learned, is very plausibly accounted for. About the beginning of July, 1608, large drops of what was then generally termed "the bloody shower" were observed in the vicinity