256 E. II. L. Scliivarz—Hot Sprinc/s. 



been calculated that the pressure on the earth's surface was 327 

 times that at present exerted,^ and, therefore, much water-vapour 

 must have been forced into the liquid rock-mass. If the principle 

 of occlusion is confirmed, then the molten magma must have been 

 able to take in far greater quantities than that which would be due 

 simply to pressure. 



However this may be, away went the moon into space, and 

 immediately both the enormous pressure of the earth's atmosphere 

 was removed and the mass was cooled below the expulsion point. 

 The surface of the moon then became subjected to enormous volcanic 

 activity, sufficiently violent, as some have imagined,- to throw out 

 materials beyond the attraction of itself, and which are only now 

 occasionally falling on our earth in the form of meteorites. What 

 became of the water- vapour? If lai'ge quantities of water are con- 

 tained in molten rock, as much, for instance, as comes out in the 

 eruptions of Vesuvius, would there not be some trace of water on the 

 moon, seeing that practically the whole of the surface is one vast field 

 of volcanoes ? One can account for much by the evaporation into 

 space and attraction by the earth, but an entire hydrosphere to 

 disappear and leave no ti'aces behind seems impossible. On the 

 other hand, if we imagine that the moon only took away a small 

 amount of water occluded in the molten rock, then we have 

 a quantity which can be more reasonably treated in this way. The 

 form of the lunar volcanoes approaches that of the quiet caldei-a- 

 form of which Kilauea is the type on earth, but we cannot attach 

 much weight to an argument based on mountains that one can 

 only see and which we cannot ascend hammer in hand. 



I am painfully aware of the weakness of much of my reasoning, 

 but most of this is due to the want of knowledge of the fundamental 

 facts of earth-structure. The stresses and strains in a ship of war 

 are known in the smallest detail, but those existing on the earth 

 are little known, although the comparative times during which the 

 two have been under observation are monstrously disproportionate. 

 If geologists could start from the beginning with a certain knowledge 

 that the earth cooled from the centre, and that the whole is in 

 isostatic equilibrium, it would not be possible to be in doubt on such 

 a subject as hot springs ; but are not these two facts, as I might 

 almost call them, still in dispute ? 



If we descend to the bottom of a mine on the Rand one is 

 astonished at the coolness of the workings, as compared with what 

 would naturally be expected from the rate of increase of under- 

 ground temperature that is usually assumed, that is, 1° F. for 

 every 50 or 60 feet ; and it is a well - established fact that in 

 many mineral countries, like Minas Geraes in Brazil, the rate 

 of increase is very small. A study of the British Association 

 Eeports on underground temperature leaves one with a sense of 

 despair : how are such divergent results to be sorted out and 

 explained ? If one is to regard the earth as a rigid structure,. 



1 Rev. 0. Fisher: " Physics of the Earth's Crust," 1899, p. 148. 



2 Sollas: Pres. Address, British Association, Bradford, 1900. 



