ANNIYEESAET ADDEESS OF THE PEESIDENT. Kx 



an enemy in buckram in order that lie may conspicuously give him 

 the coup cle grace ? He urges, for example *, the impossibility of 

 an igneous rock causing by heat alone the production of crystalline 

 minerals in the mass of an adjoining clay-slate, and cites various 

 examples where not a single felspar crystal has been produced in a 

 shale acted upon by fire for a great number of years. Eut here, 

 and in many more instances, it would seem that he assumes the 

 scene of action to have been at the very surface of the earth, 

 whilst no educated geologist would dream of accounting for the 

 crystalline alteration of rocks at their contact, except by introducing 

 the condition, of which we so often have other ample evidences, 

 of the deeply buried position of such rocks at the time of action, 

 ^o one has more ably than Bischof proved the permeation of water 

 through the minutest fissures and pores of rocks and minerals ; and 

 no one therefore better knows that every reasonable plutonist must 

 necessarily^ infer that the stony masses, when sunk to a depth of thou- 

 sands of feet beneath other strata or beneath the ocean, are more or 

 less saturated with water. He objects, again, that suffioni and 

 water vapours, in a number of instances cited, do not effect, as they 

 ought to do by " the favourite hypothesis," the conversion of sedi- 

 mentary strata into ciystalline rock. But to satisfy the conditions 

 exacted by a fair version of plutonism, these vapours ought not to 

 escape freely, as such, from fissures at the surface, but should be 

 pent up and closed in so as to sufiuse the whole mass of the mate- 

 rials on which we imagine them to produce an effect. Bischof has 

 been one of the foremost t, following Gehlen, Mitscherlich, and G. 

 Hose, to show that many substances crystallize out of an amorphous 

 mass without their component parts being previously thoroughly 

 dissolved ; and if this be the case at the surface and at the ordi- 

 nary temperature, our author is surely not the man to doubt the 

 increased general heat of a reg-ion some thousands of feet below the 

 surface, nor the intenser chemical action which may be expected 

 under such conditions of higher temperature. 



Some few geologists, carrying out the views of Bischof to an 

 extent that would have almost satisfied Werner himself, occasion- 

 ally reiterate the old objection that an ig-neous origin is incom- 

 patible with the presence of water, either free in the rock or 

 combined with other substances as hydrated minerals. The observer 

 who has watched a volcano in fall eruption, or even dimng its milder 

 phases, is not, I believe, likely to run into this fallacy. If any 

 one substance is erupted on a stupendous scale, it is surely water. 

 The vast balling volumes of steam that come bursting up in quick 

 succession through the seething lava of the crater tell at once of 

 the great bodies of water which form a principal agent in the 

 activity of the vent, and of the manner in which the melted stony 

 matter below must be suffused with it in more or less notable 

 proportions. The ingenious microscopical observations of Mr. Sorby 

 show us how the minute pores of crystalline rocks may enclose it 



* Chem. and Phys. Geol. vol. ill. p. 71. 



t Lehrbuch d. chem. u. phys. Geol. (1st Germ, ed.) vol. ii. p. 332. 



