K. MECHANICS AND ENGINEERING. 411 



forty years ago, has become completely bleached out, and full 

 of small cracks, while for the previous forty centuries during 

 which it stood in Egypt no change had been produced. 8 C\ 

 June 23,199. 



NATIVE HYDRATE OF SILICA. 



An interesting mineral substance, capable of many import- 

 ant practical applications, found in the department of Ar- 

 dennes, in France, has been brought to the attention of the 

 Academy of Sciences in Paris. This is known in the country 

 as gaize or dead stone, and lies at the base of the cretaceous 

 formation, covering the clay of the Gault, and forming beds 

 in some places of over one hundred yards in thickness. The 

 material is soft and very light, of a specific gravity of only 

 about one and a half, grayish in color, and has been found by 

 analysis to contain more than one half its weight of gelatin- 

 ous or hydrated silica, the remainder being composed of sili- 

 cate of iron, alumina, potassa, and magnesia, as also some clay 

 and fine quartzose sand. Many important industrial applica- 

 tions have already been made of this material, and others 

 have been suggested. It can be cut readily with a knife or 

 saw into thin plates or slabs of any desired size or shape, and 

 can easily be fashioned into any pattern. Exposed to the air 

 for a time it gradually becomes harder, and finally attains a 

 condition of great durability, especially if subjected to a red 

 heat, which increases its density to some extent without con- 

 tracting the material very greatly, and makes it very suita- 

 ble for the manufacture of crucibles, fire-brick, and other sub- 

 stances intended to resist the action of heat. It can also be 

 used in the preparation of certain valuable cements and mor- 

 tars, as also in making soluble glass. A somewhat similar 

 mineral, found in large quantity in the south of France, called 

 Bauxite, is likewise a hydrate of alumina, and is used largely 

 as a refractory material. It is also worked in large quantity 

 in the manufacture of aluminium, aluminate of soda, and pure 

 sulphate of alumina. 6 J3, Jlarch 21, 1870, 581. 



KILLING WHALES BY CANNON. 



The inventive genius of America has of late years been di- 

 rected very largely toward improved modes of capturing fish, 

 in which, not satisfied with the comparatively rude methods 



