MECHANICS AND USEFUL ARTS. 73 



erally practised, consists in mixing 1 with the preparation of gold and 

 protonitrate of mercury, a certain quantity of subnitrate of bismuth, 

 which serves as a flux, and allows the metal to be burnt into the por- 

 celain. M. Grenon's process, however, consists in the successive 

 application of two layers of o-old, each having a special flux, and in 

 different proportions. The first layer is burnt in at a high tem- 

 perature, after which it is polished with rotten-stone, and on it is 

 laid a thin coating of mercury-gold, which is prepared and burnt in 

 the ordinary manner. This gilding is easily burnished, takes a fine 

 polish, and is not injured by friction from hard bodies. London 

 Mining Journal, May 4. 



NEW PROCESS FOR ORNAMENTING GLASS. 



A FEW years since a discovery was announced by which a deposit 

 of silver from its solution in nitric acid was made, by the action of the 

 essential oils of cassia and cloves'. Unfortunately, however, time has 

 proved that the silver thus deposited on glass in a few months becomes 

 reconverted to a salt, covering the glass with dirty brown spots. 

 But a new process has just been introduced by Mr. Kidd, of Poland 

 Street, in which, by the application of an amalgam of mercury and 

 platinum, a mechanical deposit is effected, so that the discoverer has 

 been able to represent every description of fruits and flowers, by en- 

 graving them on the under side of the glass. When silvered, they 

 appear as if in relief, or raised on the outside surface. So accurate 

 is the process of engraving, by a number of minute needles in the 

 lathe, that any lace-pattern or embroidery may be represented with the 

 utmost precision. London Mining Journal, April 13. 



NEW MINERAL PAINT. 



WITHIN a comparatively recent period, Mr. John L. Skinner, of 

 Springfield, Mass., has succeeded in manufacturing from a peculiar soft 

 shale, belonging to the sandstone deposits of the Connecticut valley, 

 a valuable mineral paint, which is fully equal, if not superior, to the 

 celebrated mineral paint found near Akron, Ohio.* It is of different 

 shades of slate, freestone, drab, and umber, and where those shades are 

 desired is particularly valuable, as it not only has all the body and beau- 

 ty of lead paint, but surpasses it in durability. Its chief excellence 

 consists, however, in its power to resist the action of fire and water. 

 After being applied and exposed to the air, it becomes gradually indu- 

 rated, so as to present in time a perfect slate surface. The coating 

 of paint when dry is susceptible of a very high polish, and has been 

 used with great success on carriages and like work. For dark sur- 

 faces, this paint will, we think, be superior to any other material 

 now in use. The application of the material as a pigment is new, 

 and in a scientific point of view exceedingly interesting. Specimens 

 of wood painted with this mineral, of a fine polish, were exhibited at 



* See Annual of Scientific Discovery. 1S50. p. 93. 



