188 Analysis of Scientific Books. 



thread of pure quartz. 3dly, The granite of the veins, say 

 they, belongs to that species of granite which Lasius and other 

 mineralogists have styled regenerated granite. This granite 

 proceeds according to them, from the carriage of the granitic 

 particles by means of rains, which, having detached them from 

 the mass of granite, has dissolved and then deposited them in 

 the clefts of the schistous rock, where these elements, having 

 reunited, crystallized and reproduced a new granite in veins. 

 This hypothesis would have more probability, were the sub- 

 stance in question more soluble in water than are the elements 

 composing granite. But what renders it utterly inapplicable to 

 the present subject is, the circumstance already noticed, of the 

 perfect identity which exists between the granite of the mass, and 

 the granite of the veins ; an identity such, that it is impossible, 

 even by the most minute examination, to trace a line of demarka- 

 tion between the mass and the vein ; whence it appears evi- 

 dent, that both the one and the other have been formed at the 

 same moment and in the same way. 4th, In order to conci- 

 liate the system of Werner with the introductory appear- 

 ances presented by these celebrated veins, it has been pre- 

 tended that they were veins contemporaneous with the rock 

 which they traverse. Let us see if the descriptions which the 

 Wernerians themselves give of contemporaneous veins, accords 

 with Mr. Necker's accurate description of the veins of Tor-nid- 

 neon. " The oldest veins in a mountain," says Jameson, 

 (Geognosy, p. 236,) " are those composed of nearly the same 

 materials as the strata they traverse, and in which no distinct 

 seam of separation is to be observed between their sides and 

 walls ; on the contrary, the substance of the vein is to be ob- 

 served mixed with, and passing into, that of the rock ; and it 

 wedges out in every direction in the mass of rock ; thus shew- 

 ing tliat it has not been filled from above or below, but is, as it 

 were, a secretion from the rock itself. Such veins are deno- 

 minated contemporaneous, because they appear to have been 

 formed almost at the same time with the rock in which they 

 occur." Mr. Jameson then proceeds to cite Tor-nid-neon, as 

 an illustration. But Mr. Necker says, and we think justly, that 

 the characters which distinguish contemporaneous veins do not 

 agree in any respect with the veins of Tor-nid-neon. In fact, 

 they are not enveloped on all hands with the mass of schist, 

 and they do not terminate on every side in a point, since the 

 largest part of the vein opens itself always wider towards, the 

 mass of granite; while they form but a single point at the place 

 farthest removed from this mass. The substance (wall) of the 

 vein, is very different from that of the rock ; for the one is a 

 granite composed of feldspar, quartz and mica, the other a 

 slate composed of clay and quartz. The separation between 

 the two rocks is so neat and decided, that very few specimens 



