180 



in granite, which he does by shewing that the average 

 analysis of granite gives more quartz than is necessary to the 

 definite constitution of its ingredients ; that these have crys- 

 tallized from fusion, in the order quartz, mica, fellspar : and 

 that by the successive expansion of each set of crystals, the 

 residual quartz has been pushed from the surfaces of cooling, 

 towards the central and hottest parts of the mass, there 

 forming quartz veins. 



It is suggested; that the expansion produced by sudden 

 crystallization (of which instances are not wanting) may give 

 rise to earthquakes ; that the exact filling of whyn dykes, 

 notwithstanding the contraction on cooling of the dyke and 

 its walls, must be due to the same cause. The principle is 

 then carried to the solution of some cases of atmospheric 

 degradation. The Yorkshire flagstone desquamates pa- 

 rallel to the wrought surface, and across its lamina. This 

 arises from induration, and crystallization of its argillo- 

 calcareous cement, which increases in volume, and splits off 

 the desquamated portion. The same is the case with the 

 onion stone of the Causeway — both desquamate by air and 

 moisture, without the agency of frost. Lastly, it is shewn, 

 that this expansion in volume does not always necessarily 

 infer disruption. 



The author intends his paper only as an indication of a 

 wide class of forces, as yet little considered or applied by 

 the geologist, and which, although from the present condition 

 of geology as a science they cannot be often estimated, must, 

 in its future progress, form an important element of connexion 

 in all its greater problems. 



Mr. Samuel Ferguson read a paper, entitled " Remarks 

 on the late Publication of the Society of Northern Anti- 

 quaries." 



The object of this paper was to add some corroboratory 

 evidences to the fact established in the Antiquitates 



