EXPERIMENT IN MINERALOGY. 255 



advantage and not a hindrance, and need not therefore 

 be excluded either in the laboratory or in nature (12). 



EXPERIMENTS ON THE ORIGIN OF MINERALS. 



But nowhere is the want of experiment more felt than 

 in the question of mineral genesis. 



The complaint used to be that experimental geology 

 could scarcely expect success owing to our inability to re- 

 produce the enormous pressures and temperatures which 

 have prevailed during the natural production of minerals, 

 and a still greater difficulty was supposed to be the great 

 lapse of time required by the processes of nature. 



In reality, however, these objections were many years 

 ago removed by such discoveries as that of cassiterite in 

 the antlers of deer in the Cornish tin works, of gold and 

 crystalline pyrites in the woodwork of old mine-galleries, of 

 crystalline zeolites in the masonry of the Roman springs at 

 Plombieres, and of minerals resulting from the decomposi- 

 tion of coins of comparatively recent date (13). 



If the natural conditions can only be reproduced in the 

 laboratory there is no reason why minerals which have in 

 a score of centuries attained sufficient dimensions to satisfy 

 the curators of museums should not be reproduced as micro- 

 scopic crystals in as many weeks or even days. 



Ebelmen, Senarmont and Daubree, to mention only a 

 few of those who have occupied themselves with mineral 

 synthesis, have prepared a large number of minerals in 

 various ways ; at first but little attempt was made to 

 realise the conditions of nature, but by degrees higher 

 temperatures and greater pressures were employed, until 

 it became possible to reproduce many of the silicates which 

 are characteristic of volcanic lavas and igneous rocks. 

 These researches were prosecuted with much zeal by the 

 French chemists to whom the development of mineral 

 synthesis is mainly clue, and one striking result of their 

 experiments has been to demonstrate the important part 

 played by such elements as chlorine, fluorine and nitrogen, 

 even though they do not enter into the composition of the 

 final product. 



