126 Professor Bischof on the Origin of 



than a quarter of an inch thick, and have a great dip north- 

 wards, whereby the granite appears perfectly stratified, sub- 

 divided into layers of from two to three feet in thickness. The 

 unaltered granite is quite similar to that at the point just 

 mentioned, and very liable to weather. In the vicinity of 

 the quartz veins it does not weather. This arises, no doubt, 

 from the impregnating quartz having stopped the pores, so 

 that no water could penetrate afterwards to cause decomposi- 

 tion. 



Such quartz veins, of an eighth to a quarter of an inch wide, 

 forbid the most distant thought of formation by heat. v. 

 Dechen and v. ffiynhausen also found in a quartz vein of a 

 foot in width, near Mousehole, masses of a greenstone-like 

 killas, of a foot long, as far as the vein traversed this for- 

 mation. These masses of adjacent rock could not have ex- 

 isted in so great a mass of quartz, if it had come in contact 

 with them in a state of fusion. It is as little to be thought 

 of that the quartz, when it impregnated the granite of the 

 adjacent rock, was molten ; for, on the one hand, it is incon- 

 ceivable how a substance which, like quartz, is much less 

 fusible than granite, could impregnate it ; and, on the other 

 hand, if we did assume that the quartz and granite were 

 fused together, a granitic mass must have resulted again 

 after the gradual cooling, without the felspar and mica di- 

 minishing in any considerable degree. In this latter case, 

 the thin quartz strings of the veins would naturally have run 

 together with the granite ;.and, after gradual cooling, there 

 would have been found in them the same substance as in the 

 adjacent rock, and thei'e would not have crystallized from it 

 pure quartz. 



If, on the other hand, we assume that the quartz entered the 

 vein fissures in a watery solution, all appearances may be very 

 naturally explained. In the first place, the penetration of a 

 watery solution into so compact a rock as granite, is much more 

 easy to conceive than that of a molten, however liquid, mass. 

 The watery fluid always maintains its liquidity, and if it re- 

 main for a lengthened period in contact with a rock, however 

 little porous, it will gradually penetrate far into it, in conse- 

 quence of its capillarity. A molten fluid, on the other hand, 



