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Improved modification of a new electrotype process
420
Practical and Theoretical Mechanics and Chemlslry.
This phenomenon has particularly attracted the attention of M. Arago, who is of opinion that an opaque atmosphere may be produced at will, and thereby lead to the solution of most important problems on the polarization of light, which have hitherto not been resolved tbr want of the means of observation. The discovery of the chlorous acid is a fact of high importance. It completes the series of the combination of the chlorine and oxygen, and establishes an analogy the more between these compounds and the corresponding compounds of azote. Mining Jour.
Improved Modification of a New Eleetrot~jpe Process. 132/M. N ~ : w s ~ . A discovery has been recently made of etching copper plates, by first gilding them by the electrotype, and then delineating the drawing through the coat of gold to tile copper. I tried the gilding process several times, but could not succeed in producing a firm coat of metal; and I am acquainted with many scientific gentlemen who arrived at the same result--namely, a dirty black powder, easily rubbed off, instead of the "glillering rz~etallie su~2face oJ' incoml)a~'able beau@," as it has been designated by some. Indeed I am half incliued to doubt that such a thing has ever been accomplished. M y trials with the " n o b l e " metals proving in every case a decided failure, I thought of trying what could be done by means of the eupreous deposit, as I always tbund it perfectly pnre and firm, provided, only, care were taken in conducting the process. My first experiment proved quite successful; the subject of it was an ordinary steel plate. I covered it with a thin film of copper, which I afterwards etched, and bit up with dilute sulphurie acid. Far finer and closer lines can be ibrmed oll this ground than on that in general use at present, which arises from the latter being required to be laid comparatively thicker on, which, together with its property of adhering to the poit~t of the tool, during the process, sometimes sends a whole body of fine line-work into a broken unmeaning mass. What I consider the greatest advantage attending worldng on a metallic "ground," is, that after the effect, &e., is bit in, the plate can again undergo the same process, if the resulting etching be not satisfactory--an object not to be attained by the employment of grounds of a w a x y or resinous nature. Such grounds always require to be totally removed before the picture can be pronounced perteet--at least as regards the etching; and if the same be found, on inspection, to be not of the requisite degree of color, or depth of tone, the touching up is attended with labor and uncertainty. A plate furnished with a metallic ground, can, however, be bit deeper, even afler a proof has been printed from it, the coat of metal, of course, being allowed to remain on the plate. Mech. BIag.
i?eme@ for .Spontaneous Combustion of Coals. Captain Carpenter, of Her Majesty's steam frigate Ge~2ser,has suggested the following remedy for spontaneous combustion.
Practical and Theoretical Mechanics and Chemlslry.
This phenomenon has particularly attracted the attention of M. Arago, who is of opinion that an opaque atmosphere may be produced at will, and thereby lead to the solution of most important problems on the polarization of light, which have hitherto not been resolved tbr want of the means of observation. The discovery of the chlorous acid is a fact of high importance. It completes the series of the combination of the chlorine and oxygen, and establishes an analogy the more between these compounds and the corresponding compounds of azote. Mining Jour.
Improved Modification of a New Eleetrot~jpe Process. 132/M. N ~ : w s ~ . A discovery has been recently made of etching copper plates, by first gilding them by the electrotype, and then delineating the drawing through the coat of gold to tile copper. I tried the gilding process several times, but could not succeed in producing a firm coat of metal; and I am acquainted with many scientific gentlemen who arrived at the same result--namely, a dirty black powder, easily rubbed off, instead of the "glillering rz~etallie su~2face oJ' incoml)a~'able beau@," as it has been designated by some. Indeed I am half incliued to doubt that such a thing has ever been accomplished. M y trials with the " n o b l e " metals proving in every case a decided failure, I thought of trying what could be done by means of the eupreous deposit, as I always tbund it perfectly pnre and firm, provided, only, care were taken in conducting the process. My first experiment proved quite successful; the subject of it was an ordinary steel plate. I covered it with a thin film of copper, which I afterwards etched, and bit up with dilute sulphurie acid. Far finer and closer lines can be ibrmed oll this ground than on that in general use at present, which arises from the latter being required to be laid comparatively thicker on, which, together with its property of adhering to the poit~t of the tool, during the process, sometimes sends a whole body of fine line-work into a broken unmeaning mass. What I consider the greatest advantage attending worldng on a metallic "ground," is, that after the effect, &e., is bit in, the plate can again undergo the same process, if the resulting etching be not satisfactory--an object not to be attained by the employment of grounds of a w a x y or resinous nature. Such grounds always require to be totally removed before the picture can be pronounced perteet--at least as regards the etching; and if the same be found, on inspection, to be not of the requisite degree of color, or depth of tone, the touching up is attended with labor and uncertainty. A plate furnished with a metallic ground, can, however, be bit deeper, even afler a proof has been printed from it, the coat of metal, of course, being allowed to remain on the plate. Mech. BIag.
i?eme@ for .Spontaneous Combustion of Coals. Captain Carpenter, of Her Majesty's steam frigate Ge~2ser,has suggested the following remedy for spontaneous combustion.