94 Prof. Hare's Rationale on the Difficulty of separating 



existence of such alloys of the metals of the earths as may burn 

 into lava in the interior, the whole phenomena may be easily 

 explained from the action of the water of the sea and air on 

 those metals ; nor is there any fact or any of the circumstances 

 which I have mentioned in the preceding part of this paper, 

 which cannot be easily explained according to that hypothesis. 

 For almost all the volcanoes in the old world of considerable 

 magnitude are near, or at no considerable distance from the 

 sea : and if it be assumed that the first eruptions are produced 

 by the action of sea water upon the metals of the earths, and 

 that considerable cavities are left by the oxidated metals thrown 

 out as lava, the results of their action are such as might be an- 

 ticipated ; for after the first eruptions, the oxidations which 

 produce the subsequent ones may take place in the caverns 

 below the surface; and when the sea is distant, as in the vol- 

 canoes of South America, they may be supplied with water 

 from great subterranean lakes ; as Humboldt states that some 

 of them throw up quantities of fish. 



On the hypothesis of a chemical cause for volcanic fires, and 

 reasoning from known facts, there appears to me no other ade- 

 quate source than the oxidation of the metals which form the 

 bases of the earths and alkalies ; but it must not be denied that 

 considerations derived from thermometrical experiments on 

 the temperature of mines and of sources of hot water, render 

 it probable that the interior of the globe possesses a very high 

 temperature : and the hypothesis of the nucleus of the globe 

 being composed of fluid matter, offers a still more simple so- 

 lution of the phaenomena of volcanic fires than that which has 

 been just developed. 



Whatever opinion may be ultimately formed or adopted on 

 this subject, I hope that these inquiries on the actual products 

 of a volcano in eruption will not be without interest for the 

 Royal Society. 



XIV. Rationale of the Difficulty of separating Plane Surfaces 

 by a Blast, in certain Cases. By R. Hare, M.D. Professor 

 ofChemistiy in the University of Pennsylvania.* 



THE phenomenon above alluded to, is usually illustrated 

 by means of two discs, into the centre of one of which, a 

 tube is fastened, so that on blowing through the tube, the 

 current is arrested by the other moveable disc. Under these 

 circumstances, the moveable disc is not removed as would be 

 naturally expected. Supposing the diameter of the discs to 



* Communicated by the Author. 



be 



