209 



extensively; an action which I have also elsewhere 

 shown to have been sometimes exerted throughout 

 the felspar of granite veins. 



But admitting now, as it cannot be denied, that 

 micaceous schist was deposited, like the secondary 

 micaceous sandstones, from water, and consolidated 

 by the same means, it presents characters which can- 

 not be accounted for by this process. If its flexibility 

 has not been the consequence of heat, which I have 

 elsewhere attempted to prove that it has, the pecu- 

 liarities of its crystalline texture and occasional con- 

 tents cannot be explained, without admitting that it 

 has been exposed to a heat, sufficiently intense and 

 sufficiently durable, to permit these minerals to be 

 formed in the same manner as they are in granite 

 and in the volcanic rocks. The condition and ex- 

 istence of garnet, hornblende, tourmaline, staurotide, 

 and other minerals, are inexplicable by any mode of 

 watery deposition, and still less by any subsequent 

 crystallization from water. 



This argument, which applies generally to all the 

 stratified rocks that contain superfluous minerals, 

 crystallized within them, and not rounded by trans- 

 portation, is illustrated by what happens in cases 

 where strata have been exposed to the action of trap 

 rocks, and where the influence of heat is more gene- 

 rally admitted. Thus, at Poussac, near Bagnieres, 

 there are limestones which have been affected, and 

 indurated, or otherwise changed, by the contact of 

 basalt; and it is here remarkable, that while the purer 

 ones are simply rendered crystalline, the earthy pro- 

 duce made, actinolite, and tremolite. This is exactly 

 analogous to what happens where granite invades 

 primary and earthy limestones; and where the partial 

 change, and similarly partial presence of such minerals, 



VOL. I. F 



