delations of Trap-Rocks with Ores of Copper. 27 



such considerable quantities of peroxide of anhydrous iron ; 

 while we cannot well conceive the iron deposited from waters, 

 in any other state than that of hydrated peroxide \ When 

 we examine the immense quantity of oligistic iron dissemi- 

 nated through red-coloured arenaceous formations, we can 

 form only two hypotheses ; either this mass of peroxide has 

 been derived, like the other arenaceous elements, from the 

 pre-existing rocks ; or, it has been superadded, by means of 

 special phenomena, in those same basons where the sedimen- 

 tation took place. The first of these suppositions is scarcely 

 admissible ; and we are led, by every thing that has been 

 previously said, to have recourse to the phenomena of sub- 

 terranean emanations, contemporary with the deposits, and 

 mingling their products with those of the sedimentation. 



In suppoi*t of this hypothesis, we may mention the remark 

 made by M. Elie de Beaumont, that the presence of stratified, 

 dolomite, gypsum, anhydrite, and rock-salt, almost always 

 concurs with the red colour of the deposits. Now, all have 

 nearly agreed in regarding all these substances as origina- 

 ting in metamorphic actions contemporaneous with the de- 

 posits in which they are formed. 



Thus, throughout the whole duration of geological times, 

 the interior of the globe should appear to us as a centre of 

 continuous emanations, which have sent enormous masses of 

 iron to the surface ; these emanations mingling their anhy- 

 drous products, sometimes with those of sedimentation, at 

 other times interposing themselves under the form of concen- 

 trated repositories, in the rocks elevated by the eruptive 

 masses. — Amedee Burat* 



* From Annales des Mines, t. xiii., p. 351-378. 



