538 Scrope — On the Internal Fluidity of the Globe. 



moderate, distances from the outer surface. All this I have myself 

 urged at length on the consideration of geologists (see pp. 265-275 

 of my work on Volcanos, Longman, 1862), adding that, in my opinion, 

 the existence of such vesicles, side b}'- side, or even one above the other, 

 — sometimes solidified by increase of pressure,then again, perhaps, liqui- 

 fied by its diminution, or increments of caloric reaching them laterally or 

 from beneath by conduction, will account for, and, indeed, is proved 

 by, the phenomena of volcanos, earthquakes and superficial elevations 

 and depressions, I do not, however, intrude on yonr pages for the 

 purpose of claiming the origination of these views, so much as to call 

 the attention of your readers to the particular point on which the 

 whole theory hinges, namely the enormous 'pressure to which every 

 portion of the heated interior of the globe must be subjected ; and 

 this not merely from the weight, or contraction on cooling, of its 

 outer belt, but also from the vast internal tension of its every part, 

 caused by its tendency to expansion through intense heat, and this 

 whether in a solid, fluid, or gaseous state. More particularly must 

 such tension be intensified if, as there is every reason to believe, the 

 subterranean matter is permeated with water, perhaps occasionally 

 solidified by pressure, although at the highest conceivable tem- 

 perature. 



This consideration seems to have been entirely overlooked by 

 those who have supposed the earth's interior to be necessarily fluid, 

 because at a temperature exceeding that which would reduce to fluid 

 fusion in open air all the materials of its outer crust. Let this tre- 

 mendous pressure be locally relaxed by the fissuring and elevation 

 of the resisting crust, as has evidently happened along the lines of 

 mountain chains, and portions of the solid mass below must imme- 

 diately pass into the fluid state — giving rise to the igneous intrusive 

 rocks so generally found within and beneath them, "and the water 

 contained in them, assuming as it ascends a gaseous state, will, under 

 favourable circumstances of facility of exit, cause that ebullition of 

 lava in which a volcanic eruption essentially consists." 



This last passage I extract from another paper in your last number 

 by Mr. Fisher (p. 493), who speaks of his view as for the first time 

 proposed, and does not seem to be aware that this precise theory of 

 the nature of Volcanic and Plutonic action is not only fully developed 

 in the last edition of my work on Volcanos, but is to be equally found 

 in that which bears the date of 1826. 



In pp. 277 and 287 of the second edition I have shewn how the 

 expansion of subterranean matter must occasion prolonged fissures 

 through the overlying rocks, by which the intumescent matter will 

 often find a vent, sometimes thrusting up the rocks on either side in 

 dislocated or crumpled masses, owing to the squeeze or jam oc- 

 casioned by lateral or rather diagonal pressure ; sometimes, where 

 the heated matter has risen sufficiently to communicate with the 

 open air, ejecting it in floods of lava and exf)losions of steam. Hence 

 the general parallelism and occasional coincidence of linear Vol- 

 canos and of mountainous elevations ; the intervening flatter areas 

 between these eruptive ranges undergoing at the same time either a 



