152 Geological Society : — 



posed for a period of one minute to the direct rays of the sun, at 

 noon, on a very clear day in the month of March. 



The extraordinary calorific and illuminating powers of the 10-inch 

 machine are all the more remarkable from the fact that they have 

 their origin in six small permanent magnets, weighing only 1 lb. each, 

 and only capable, at most, of sustaining collectively a weight of 60 

 lbs. ; while the electricity from the magneto-electric machine em- 

 ployed in exciting the electro-magnet was of itself incapable of heat- 

 ing to redness the shortest length of iron wire of the smallest size 

 manufactured. 



The production of so large an amount of electricity was only ob- 

 tained (as might have been anticipated by the physicist) by a cor- 

 respondingly large amount of mechanical force ; for it was found 

 that the large electro-magnet could be excited to such a degree that 

 the strong leather belt was scarcely able to drive the machine. 



When the electro-magnet of the 10-inch machine was excited by 

 means of the 2^-inch magneto-electric machine alone, about two- 

 thirds of the maximum amount of power from the 10-inch machine 

 was obtained. 



From a consideration of the combined action of the magneto- 

 electric and electro-magnetic machines, the author points out a re- 

 markable analogy, subsisting between the operation of the static 

 forces of magnetism and of cohesion in modifying dynamical phe- 

 nomena, which throws additional light upon the nature of the mag- 

 netic force. 



On reviewing and comparing the whole of the analogous phe- 

 nomena manifested in the operation of the magnetic and cohesive 

 forces under the varied conditions to which the author invites atten- 

 tion, it appears to him that magnetism is a mode of the force of 

 cohesion, or is, if the term be allowed, polar cohesion acting at sen- 

 sible distances, the equivalent of magnetic force being obtained at 

 the expense of an equivalent of ordinary cohesive force (in an axial 

 direction) so long as the iron continues to be magnetized. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxxi. p. 548.] 



May 23, 1866.— Prof. A. C. Ramsay, F.Pv.S., Vice-President, 



in the Chair. 

 The following communications were read : — 

 1. '« Notes on the Geology of Mount Sinai." By the Rev. F. 

 W. Holland. 



The physical features of the peninsula were described as exhibit- 

 ing in the north an extensive tableland of limestone of Cretaceous 

 age, supported and enclosed on the south by a long range of moun- 

 tains composed of syenite, porphyries, and schistose rocks. Near 

 Jebel Serbal is a mountain of Nurnmulitic limestone ; and a lime- 

 stone, apparently of more recent date, occurs near Tor and Ras 

 Mohammed. The author further stated that in some parts of the 

 peninsula the syenitic mountains are capped by horizontal beds 

 of sandstone of considerable thickness, which arc unaltered at 



