THE DIAMOND AND OTHER PRECIOUS STONES. 363 



polish, transparence, and crystallization render them suitable for gems. 

 We may afterward discover the method of coloring them, which would 

 not seem a verj^ difficult task, from the fact that the coloriug-matter is 

 always a foreign substance, and that, in many cases, gems have already 

 been artificially colored. Ebelman, by evaporating ether from silica, 

 has obtained beautiful specimens of paste, exactly resembling opal. 

 Though man may never be able to discover all the processes of nature in 

 the production of objects of curiosity or practical utility, yet he is every 

 day inducing her to disclose some of the secrets of her operations, either 

 as she reveals them spontaneously in the changes of the e^irh or is 

 forced to repeat them under the coercion of Iu>t own agents — heat, light, 

 and electricity. 



