T. Mellard Reade—The Age of the World. 151 



the result of atmospheric waste and volcanic emissions and intrusions ; 

 that this composite body, called the crust, has, from time to time, 

 throughout all geologic ages, been not only broken up, but heated 

 matter has been injected into it^ or thrown over it; and that this has 

 . occurred at one time or another over the whole of the known globe. 



Not only has this been the course of events, but the great mountain 

 chains — the Andes, the Alps, the Pyrenees, and the Himalayas^ — 

 have been thrown up at a comparatively recent time, geologically 

 speaking, so that the more we restrict the age of the world, the hotter 

 should the strata be under those great continents on which these 

 mountain chains rest. 



To get out of this dilemma is impossible ; for we cannot consider 

 these volcanic outbursts as mere local effects, the volcanos at present 

 active being in lines thousands of miles long, the effect of deep- 

 seated forces probably connected with central heat, but, even if not, 

 fed by lakes of molten rock sufficient to set all calculations of secular 

 cooling at defiance.^ 



A study of existing volcanos also shows that molten rock at the 

 surface does not act now in the way Sir W. Thomson assumes 

 it did in his hypothetical incandescent globe. Why it should not I 

 cannot conceive. In the volcano of Kilauea, Hawaii, in the Sand- 

 wich Islands, the molten rock boils up in the crater, while waves of 

 red-hot matter dash against the surrounding cliffs, and break in in- 

 candescent spray.'' If molten rock does this now, why should it in 

 the first formation of the globe set suddenly solid from the circum- 

 ference to the centre, as required by Sir W. Thomson's theory, 

 and ever afterwards be gradually cooling as an iron shot might cool 

 from a white heat ? 



1 Prof. Judd points out, in his admirable " Contributions to the Study of Volcanos," 

 Geol. Mag. 1876, p. 211, that in the Southern Tyrol, during the Permian period, 

 " enormous masses of volcanic rock were erupted, leading to the formation of volcanic 

 mountains at least 8,000 feet to 9,000 feet high." The great " Whin Sill" has also 

 been proved by Topley and Lebour to be a vast intrusive sheet. Innumerable similar 

 examples may be quoted ; and as it is usually only by denudation we get a glimpse 

 of those volcanic rocks occupying the interior of the crust, we may be sure there are 

 many others unknown because undisclosed. 



•^ Eamsay, Geological History of some of the Mountain Chains and Groups of 

 of Europe, Mining Journal, 1875. Judd, Contributions to the Study of Volcanos, 

 pp. 133-41. 



3 As a proof of the failure at present to establish any law of increase of tempera- 

 tui-e, the remarkable temperature results in the boring at Sperenberg, near Berlin, 

 4172 feet deep, may be quoted. In this case the iirst 283 feet were in gypsum, with 

 some anhydrate, and the remainder entirely in rock-salt. Although rock-salt possesses 

 a considerably higher conducting power than even quartz, being "Olloi, and more 

 than twice that of Aberdeen granite, the rate of increase of temperature averaged 1° 

 per 51-5 feet. (British Association Report on Underground Temperature, 1876, 

 p. 206.) If the rates of increase should be inversely as their conductivity, on the 

 supposition of an uniformly cooling globe, the increase of temperature should, com- 

 pared with Mont Cenis, not be more than I'' per 200 feet. Does it not suggest that 

 the source of the heat must be nearer the surface, or that there exists beneath, some 

 mass of rock abnormally heated ? — a supposition consistent with the geological fact 

 already stated of the intrusion of heated matter into the crust of the globe and at 

 various epochs of its history. 



* Log Letters of the Challenger. 



