348 M. Amedee Burat on the 



taken place in their depth. If we take a glance at the future, 

 we may indeed expect that some new centre of production 

 will be discovered ; but it is evident that the principal re- 

 source must always be in the depth of the mines already known 

 and wrought. 



It is of great interest, therefore, to appreciate the theoreti- 

 cal principles which lead us to expect the continuation of 

 minerals in depth, and to examine the facts elicited in con- 

 sequence of the increasing depth of excavation already exe- 

 cuted. Such is the object of this memoir. 



What are the theoretical principles on which we may rest, 

 and what is the value of these principles \ Geology is the 

 only guide for the working of mines ; but we find in geology 

 numerous instances of arbitrary and abandoned theories. We 

 propose, in the first place, to shew that the theoretical views 

 cari'ied into operation in mines have been established by 

 practical observations, and that they are supported by facts 

 which cannot be questioned, owing to their number and 

 generality. 



The application of geology to the woi'king of mines goes 

 no further back than the year 1775, the time when Werner 

 beffan his lectures at the School of Mines in Freiberg. Six 

 or seven centuries of mining operations in the mines of 

 Saxony and the Hartz had, in some measure, prepared the 

 lectures of the illustrious Professor, and placed at his dis- 

 posal an enormous accumulation of practical observations. 



The neighbourhood of Freiberg alone presents many hun- 

 dred metalliferous veins, which can be studied by means both 

 of subterranean and superficial works ; the two declivities of 

 the Erzgebirge, from Altenberg and Zinnwald, as far as 

 Joachimsthal, Schneeberg and Bleistadt, furnish a still 

 vaster and more varied field of observation. In the Hartz, 

 four collections of extensive veins have been wrought in the 

 vicinity of Clausthal and Zellerfeld, and the complex net- 

 work of veins at Andreasberg has long been diligently 

 mined. These riches of the high regions of the Hartz over- 

 look a circle having numerous works scattered round its cir- 

 cumference, among which we distinguish the mines of Ram- 

 melsberg, Elbingerode, Ilefeld, Lauterberg, &c. We may 



