62 



Cincinnati Society of Natural History. 



amorphous sulphide of lead and a solution of hydrogen sulphide 

 under strong pressure. This mixture was heated to 150 degrees and 

 then as the temperature was reduced, the lead crystallized in small 

 brilliant cubes. 



Fluoriic was formed by Senarmont, in 1850, by heating the 

 gelatinous fluDrite precipitate in the presence of bicarbonate of soda 

 in a sealed tube at 180 degrees. The crystals were in the form of 

 cubic octahedra. 



Cassiterite was obtained in brilliant crystals of a brown color by 

 Daubree, in 1849. He heated to redness in a porcelain tube, water 

 vapor and bichloride of tin vapor. When lime was used instead of 

 water, the result was produced as before. 



Silver crystals were obtained by Margottet, in 1877, by the 

 reduction of silver sulphide at a temperature of 440 degrees. Gold 

 was formed in crystals of some size, in 1863, by Knoffl, who heated 

 for ten days at a temperature of 80 degrees, an amalgam of gold and 

 mercury treated with nitric acid. 



The original workers in mineral synthesis concentrated their 

 crude efforts on the formation of gem stones seeking to enrich 

 themselves rather than science. Failing in this they could see no 

 further value in the experimental formation of minerals. Though the 

 primary object of these attempts has never been attained, they have 

 contributed interesting and instructive data concerning the origin of 

 the precious minerals. The small and imperfect crystals are com- 

 mercially without value, while scientifically they are of the greatest 

 value. 



Corundum, for example, has been formed in a large number of 

 ways. Gaudin, in 1837. first obtained this substance in definite 

 crystals. His method consisted in heating at a high temperature, 

 potash alum, with or without the addition of potassium sulphate, and 

 on cooling clear crystals of corundum separated out. A more remark- 

 able method was employed by Senarmont, in 1850, who heated in a 

 closed tube at 350 degrees a mixture of chloride of alumina, azotate 

 of alumina, and water, whereby small rhombohedra were obtained. 

 Ebelmen introduced small quantities of the oxides and obtained the 

 various colors, ruby, sapphire, etc. 



Diamonds as yet have probably not been reproduced. The early 

 attempts to form them by the fusion of graphite in electric currents 

 were clearly at fault, for Brewster and Goppert discovered in the 



