AND THEIR MEETING WITH GRANITE, 95 



junction we have in view, if it does occur at the surface, will 

 most probably be found where granite meets with gneiss or 

 mica-slate, not where it meets with killas *. I have no scruple, 

 however, in presenting these speculations to the Society, al- 

 though I cannot produce direct evidence in support of them, 

 because I trust that the conjecture is sufficiently plausible to 

 merit some attention; and, above all, because it may be the 

 means of giving rise to much interesting observation, in a de- 

 partment hitherto overlooked, or in which, for want of any 

 connected system, the observations of travellers have been 

 lost. 



It will be an object of consequence, that future travellers 

 should attend to this circumstance in the Alps, where a very 

 long ridge of granite is bordered on both sides by strata. The 

 ideas just stated, not having occurred to me till long after I 

 had left that country, I can form no judgment with respect to 

 what inferences may be drawn from the state of facts which 

 are there to be seen. It is certain, that the strata of the Alps 

 are very much convoluted, as mentioned in various places by 

 M. de Saussure ; but whether these forms could reasonably 



be 



* Gneiss is found to pass by insensible degrees into granite ; that is, speci- 

 mens of every conceivable intermediate step have been found. We may then 

 conceive one stage more advanced towards granite than the rest, in which all 

 character of the original stratification is removed, and the mass may have be- 

 come wholly crystalline, but in which the peculiarity of each stratum may still 

 have left a trace of its character, in the quality of the granite thus produced 

 from it. This seems to explain the nature of a great part of the internal ridge 

 of the Alps, which is possessed, as Saussure mentions, of a stratified character. 

 This mass may, again, be traversed from within by granite in higher heat, and 

 in a state of complete liquidity, which would be more ready than the mass first 

 described, to penetrate into the neighbouring masses. Accordingly, Saussure 

 observes, that those veins, and other masses which, project from the central 

 ridge, and penetrate farthest into the neighbouring strata, are devoid of that 

 stratified character. 



