404 J. Starlde Gardner — Underground Seat. 



denude its surface, and lead to the formation of submarine areas of 

 elevation which assume the form of ridges and banks and finally dry 

 land. The movements must be infinitely complicated, but the greatest 

 depths or hollows of the ocean would be the least likely to come 

 under the influence of denudation, and would thus probably prove 

 jDermanent. As the great ocean currents are caused by the difference 

 in specific gravity of the tropical and polar waters, they must flow 

 north and south, and areas relatively free from sediment would lie in 

 the same directions, as we in fact know that the chief land surfaces 

 do. This theory agrees with most known physical facts, and it 

 would be interesting to trace it further did space permit. 



It has been objected that a solid crust could not be supported on a 

 liquid, but would break up and sink through. Lava, however, in 

 cooling, forms a crust, which is supported on the still molten mass, 

 and the crust of the earth must be, as a whole, of lighter specific 

 gravity than the fluid it rests on. 



The movements of the earth's crust are, on the whole, more com- 

 patible with a crust of 10 miles in thickness, the minimum assigned 

 to it by physicists, than with the maximum estimate of 50 miles. 



Modern engineering would not, perhaps, consider the task of 

 piercing even such a depth as 10,000 feet, at which depth boiling 

 water must be reached, an altogether hopeless one, were the stake 

 sufficiently great ; for mere artesian wells have been bored to the 

 depth of nearly a mile. London would perhaps be a very unfavour- 

 able area in which to experiment, as the upper water-bearing strata 

 are of great tliickness, and have outcrops in adjacent counties. 

 Were there any water-bearing strata however among the deep-seated 

 Paleozoic rocks, supplies of boiling water might be confidently 

 reckoned upon. The west of England would be a much more 

 favourable field, but the chances are that the neighbourhood of 

 London would be preferred, as there is still the strongest probability 

 that coal may yet be pierced at a workable depth, and the enormous 

 sum of £5,000,000 per annum paid by Londoners for its carriage 

 be thereby saved. 



It is hardly probable that danger would ensue from sinking a 

 shaft even into molten lava, were it possible to do so, and I should 

 not apprehend that any uncontrollable eruptions would ensue. Molten 

 lava habitually fills some craters for long periods at a time, and 

 remains in a constant state of ebullition. There is no need, however, 

 to essay so gigantic an enterprise just yet, as a supply of more 

 moderate heat would go far to check the rapid consumption of fuel. 

 As illustrating the possibility of obtaining such, the following 

 extracts ^ are of interest : 



"Near St. Etienne (France) a new geyser has been discovered. 

 At a depth of 1500 metres a vein of hot water was tapped, and the 

 result is an intermittent fountain which sends its water to a height 

 of 26 metres. The geyser ejects carbonic acid as well as hot water." 



"The deepest artesian well in the world is being bored at Pesth, 

 and has reached already a depth of 951 metres. The well at Paris, 

 which measures 547 metres, has hitherto been the first. The work 

 1 From "JSTature " of various dates. 



