T. Davidson — On Continental Geology. 199 



range, we shall find a cause for the general parallelism of the great 

 lines of volcanic eruption to those of the nearest mountain chains or 

 coast-lines of raised land, — a parallelism which has been often re- 

 marked, but unaccounted for that I am aware of upon any other 

 hypothesis (see Volcanos, ed. 1862, p. 309). 



One word more. If we are to suppose the water of lavas to 

 have been derived through all past time from the superficial ocean, 

 where are we to seek, it may be asked, the origin of the water of 

 the ocean itself, if not from the interior of the globe, which even now 

 sends out torrents of aqueous vapour from every rent opened through 

 its crust ? The believers in the nebular hypothesis will no doubt 

 find it in the original gaseous atmosphere left after the condensation 

 of the neuclus. But even conceding this for the bulk of the ocean, 

 still it may well be supposed that large quantities of water remained 

 " entangled" in the condensed matter. 



Without, however, looking back to the beginning of things, as too 

 many geologists are in the habit of doing, in order to explain pheno- 

 mena of daily occurrence, I think I have shown reason for the belief 

 that the water which evidently permeates the lava beneath a volcanic 

 vent, and by its violent expansion occasions an eruption, existed there 

 before the earthquakes that usually accompany the eruption began, 

 and was not suddenly introduced by the opening of fissures com- 

 municating with seas or lakes above. Whether it existed in the 

 material whence the lava is formed from the beginning, or proceeded 

 from any chemical changes in this elementary rock, or magma — or 

 had penetrated there by slow and long-continued filtration from 

 above (which is the opinion of M.M. Daubree and Fouque), T do 

 not hazard a conjecture. Our knowledge, at present, of the effects of 

 intense heat and pressure, whether chemical or mechanical, on 

 mineral substances — of the influence of terrestrial magnetism — and 

 of the nature and origin of the deeply-seated matter that composes the 

 globe, are too imperfect, I think, in the present state of science, to 

 enable us to solve such problems. But since it has become the 

 fashion, of late, among the leaders of popular geological treatises, to 

 assume as a matter of fact, beyond dispute, that the substance of the 

 globe, immediately beneath its thin superficial crust (and probably 

 to its centre), is in a state of fluid fusion, and that the access of water 

 from the sea above to this molten interior, is the exciting cause of 

 earthquakes and volcanos, I have thought it well to express my 

 reasons for entertaining doubts, to say the least, as to the correctness 

 of either hypothesis. 



Fairlawn, Cobham, April 10, 1869. 



III. — Notes on Continental Geology and Paleontology. 

 By Thomas Davidson, F.R.S., F.G.S. 

 {Continued from p. 166). 

 (Part II.) 



HAVING in my last communication presented the most recent 

 views entertained by M. Coquand, I now proceed to mention 

 those held by Monsieur Hebert, a most experienced observer, who 



