Geological Society, 299 



1213. That I might be sure of the sensibility and action of 

 the apparatus, I made such a change in one as ought upon 

 principle to increase its inductive force, i. e. I put a metallic 

 lining into the lower hemisphere of app. i., so as to diminish 

 the thickness of the intervening air in that part, from 062 to 

 O'^SS of an inch : this lining was carefully shaped and rounded 

 so that it should not present a sudden projection within at its 

 edge, but a gradual transition from the reduced interval in the 

 lower part of the sphere to the larger one in the upper. 



1214. This change immediately caused app. i. to produce 

 effects indicating that it had a greater aptness or capacity for 

 induction than app. ii. Thus, when a transferable charge in 

 app. ii. of 469° was divided with app. i., the former retained 

 a charge of 225°, whilst the latter showed one of 227°, i. e. 

 the former had lost 24'4° in communicating 227° to the latter : 

 on the other hand, when app. i. had a transferable charge in 

 it of 381° divided by contact with app. ii., it lost 181° only, 

 whilst it gave to app. ii. as many as 194°: — the sum of the di- 

 vided forces being in the first instance less^ and in the second 

 instance greater than the original undivided charge. These 

 results are the more striking, as only one half of the interior 

 of app. i. was modified, and they show that the instruments 

 are capable of bringing out differences in inductive force from 

 amongst the errors of experiment, when these differences are 

 much less than that produced by the alteration made in the 

 present instance. 



[To be continued.] 



XL. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from p. 233.] 



May 23. — A memoir entitled, a Synopsis of the English series of 

 stratified rocks inferior to the old red sandstone — with an attempt 

 to determine the successive natural groups and formations, by the 

 Rev. Adam Sedgwick, Woodwardian Professor in the University of 

 Cambridge, commenced on the 21st March, was concluded. 



Introduction. — The author, after stating what was now oflpiered to 

 the Society to be only a first approximation, involving many questions 

 of difficulty and doubt, pointed out the principles on which he had 

 undertaken the task. There are two elements of classification ap- 

 l)licable to stratified rocks of all ages, viz., physical structure and 

 order of superposition; one giving the mineralogical unity of a 

 group of rocks, the other their relative age. In addition to the two 

 former, are classifications founded on the organic remains in the 

 several groups. In the commencement of geology the last method 

 was only subsidiary to the two former. But after observations had 



