Geological Society of London. 185 



wise, he asks, can we conceive tlie strata to be thrust into a vertical po- 

 sition by a liquid from below, without the very bowels of the earth gush- 

 ing out ? Without attempting to answer this question, we may observe, 

 that when we suppose, as Mr Darwin supposes, a vast portion of the 

 earth's crust, the whole territory of Chili for example, to rest on a lake of 

 molten stone, there is considerable force in M.de Beaumont's argument: 

 — that when such a fluid is raised to the top of a mountain ten or twenty 

 thousand feet high, the pressure upon the crust which is in contact with 

 the fluid must be more than a thousand atmosjiheres ; and who, he too 

 asks, flatters liimself that he knows enough of the interior machinery of 

 volcanos, to be certain that this vast pressure, acting upon a large surface, 

 may not, by some derangement of its safety-valve, the volcanic vent, pro- 

 duce effbcts to which we cannot assign any limit ? 



In speaking of Mr Darwin's researches, I cannot refrain from expressing 

 for myself, and I am sure I may add for you, our disappointment and 

 regret that the publication of Mr Darwin's journal has not yet taken 

 place. Knowing, as we do, that this journal contains many valuable 

 contributions to science, we cannot help lamenting, that the customs of 

 the Service by which the survey was conducted have not yet allowed this 

 portion of the account of its results to be given to the world. 



Although not communicated to us, but to our Alma Mater the Roj-al 

 Society, I may notice Mr Hopkins's endeavours to throw light upon such 

 subjects as this by the aid of mathematical reasoning. The researches of 

 Mr Hopkins respecting the effects which a force from below would pro- 

 duce upon a portion of the earth's crust have already interested you, and 

 would be of still greater value, if the directions of faults and fissures 

 which result from his theory did not depend very much upon that which, 

 in most cases, we cannot expect to know, the form of the area subjected 

 to such strain. Mr Hopkins has since been emplo3'ing himself in tracing 

 the consequences of another idea, truly ingenious and philosophical, and 

 which a person in full possession of the resources of mathematics could 

 alone deal with. Some of the effects which the sun and moon produce 

 upon the earth (as the precession and nutation,) include the attraction 

 of those bodies upon the interior portion of the earth, and have hitherto 

 been deduced from the theory by mathematicians, upon the supposition 

 that the earth is solid. But what if the central portion of the earth were 

 fluid.'' What if it appeared, by calculation, that the fluid internal con- 

 dition would make the amount of the precession of the equinoxes, or of 

 the nutation of the axis, different from that which the solid spheroid 

 would give ? What if it appeared, that the precession and nutation thus 

 Ccalculatcd for a fluid interior agreed better with observation than the rc- 

 .«ult hitherto obtained by supposing the earth solid ? If this were so, we 

 .should have evidence of the earth's interior fluidity, evidence, too, of a 

 perfectly novel and striking nature. But to answer these questions is far 

 from an easy task ; the precession of the solid earth is a problem in which 

 Newton erred, and in which the greatest mathematicians of modern times 



