520 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



tion of gum, glycerine, glue, etc., in making up the plaster, 

 when the viscosity operates against crystallization. The 

 treatment of plaster with alum and sulphuric acid, as sug- 

 gested by him, and which is the most advantageous, dimin- 

 ishes somewhat its affinity for water, and thus causes it to 

 set more slowly. The minimum of water can therefore be 

 used in making it up, and, since it is perfectly anhydrous, it 

 combines with a larger quantity of the water than the com- 

 mon gypsum, dries more rapidly, and becomes very hard. 

 He also found that the caustic lime contained in plaster, re- 

 sulting from the presence of carbonate in the gypsum, exer- 

 cises a favorable influence upon its setting when mixed with 

 water, since it combines with a portion of the water, produc- 

 ing an elevation of temperature and more rapid setting, and 

 imparts a hardness doubtless due to its conversion into car- 

 bonate in the air. Common gypsum, containing 10 per cent, 

 of lime, is said to give very excellent results, as it can be 

 readily smoothed, and resists atmospheric influences better 

 than plaster alone. Landrin has even prepared cements con- 

 taining as high as 75 per cent, of lime. 13 C, JVbve?nber 1, 

 1874,1369. 



COLOR OF CHINESE BRONZES. 



A chemical examination of some Chinese and Japanese 

 bronzes of an unusually deep color, exhibited in Paris in 

 1869, has shown the existence of a much larger percentage 

 of lead than occurs in the ordinary bronzes, proving that it 

 is to this substance that the special composition and color 

 of the bronze is due. Where zinc was present in consider- 

 able quantity, it seemed rather to counterbalance the effect 

 of the lead. An alloy, composed of 5 parts of tin, 83 of cop- 

 per, 10 of lead, and 2 of zinc, proved to be exactly like the 

 Chinese bronze, and identical with it in fracture and pol- 

 ish. When heated in a muffle, it quickly assumed the pe- 

 culiar dead-black appearance so greatly admired in Chinese 

 bronzes. 21 A, Sept., 1874, 927. 



ARTIFICIAL DECORATION AND HARDENING OF SANDSTONE. 



The following process of artificially impregnating sand- 

 stone is said to be in successful operation at several German 

 stone quarries. The stone operated upon is a porous sand- 



