M. TECHNOLOGY. 503 



quartz sand, mixed with a solution of potash water-glass, of 

 which so much is added that the mass can be laid on with a 

 brush, and in greater quantity the more porous the ground. 

 The carbonate of lime may be either chalk or marble powder. 

 The quartz sand must be clean and well washed, and of even 

 grain. The mass of carbonate of lime and quartz sand to- 

 gether should be three to four times the volume of the ce- 

 ment. This, besides possessing a good absorptive power and 

 durability, is white, and in this respect is very superior to 

 some kinds which otherwise have equally meritorious quali- 

 ties. 21 A, December, 1871, 1221. 



TRANSPARENT STEREOSCOPIC PICTURES. 



A method of making transparent stereoscopic pictures upon 

 paper is thus described by its discoverer, Mr. A. von Con- 

 stant, of Lausanne. Well-sized and not too thick albumen 

 paper is made sensitive in the usual way, and the negative 

 placed upon its back i. e., the side not chemically treated. 

 The printing is done rather strongly, and the tone observed 

 by looking through the paper toward the light. The picture 

 can be conveniently colored with water- colors, and is well 

 adapted for lamp-shades, etc. 14 (7, vol. cciv., April, 1872. 



GASOLINE FOR EXTRACTING FATS. 



Dr. Vohl, of Cologne, continues to discuss the virtues of a 

 form of petroleum w r hich he calls Canadol, Canada oil, or gaso- 

 line of United States manufacturers, which he considers espe- 

 cially adapted to the extraction of fats of any kind from their 

 original sources, and their conversion into articles for the ta- 

 ble or for industrial purposes. The advantages of his meth- 

 od over that of cold and warm pressure he finds to consist 

 both in the much greater yield and in the vastly improved 

 quality, the residuum not being at all injured for use in other 

 ways. The sulphide of carbon has frequently been employed 

 by perfumers and others for extracting oily substances ; but 

 Vohl considers its use so greatly inferior to that of Canada 

 oil as not really to come in competition with it. The but- 

 ter can be extracted from the cacao-bean by this substance, 

 thereby greatly improving the quality of the prepared cocoa. 



Another application of the Canada oil is to the removal of 

 the fat from bones, leaving them as white as if bleached for a 



