Rev. W. D. Conybeare's Report on Geology. 431 



one of these points, and that very important to geological theory, ap- 

 pears to me to require further investigation ; I mean the conclusions 

 fairly deducible from the known density of the earth, as to the solid 

 structure and composition of its interior. As its density is known to 

 be considerably greater than that of a solid sphere composed of any 

 such rocks as we are acquainted with, (granite, for instance,) our 

 primd facie inference would naturally be, that the interior is solid ; 

 and that heavier materials than our ordinary rocks (such as metalli- 

 ferous masses,) enter into its constitution. But to this it may be ob- 

 jected that the rocks alluded to have in themselves a principle of elasti- 

 city and compressibility, and therefore may, under the vast pressure 

 existing in the interior of the globe, be condensed to such a degree 

 as is far more than sufficient to account for the excess of the earth's 

 density, as compared with their specific gravity, and thus still to allow 

 for considerable vacuities. To this, however, a counter argument may 

 be fairly adduced, that, as the resistance to further compression in- 

 creases with everv additional pressure, that resistance may soon, in 

 the case of these rocks, become practically infinite. A more accurate 

 examination of the whole circumstances of this problem appears 

 highly desirable. 



" It has been well observed in a very able article in a late perio- 

 dical, that ' the most conclusive argument against the fact of any dis- 

 turbance having, in remote antiquity, taken place in the axis of the 

 earth's rotation, is to be found in the amount of the lunar irregularities 

 which depend on the earth's spheroidal figure. However insufficient 

 the mere transfer of the mass of the ocean, from the old to the new 

 equator, might be to ensure the permanence of the new axis, the 

 enormous abrasion of the solid matter of such immensely protuberant 

 continents as would, on that supposition, be left, by the violent and 

 constant fluctuation of an unequilibrated ocean, would (according to 

 an ingenious remark of Professor Playfair, ) no doubt, in lapse of some 

 ages, remodel the surface to the spheroidal form ; but the lunar theory 

 teaches us that the internal strata, as well as the external outline of 

 our globe, are elliptical, theircentres being coincident, and their axes 

 identical with that of the surface, — a state of things incompatible 

 with a subsequent accommodation of the surface to a new and dif- 

 ferent state of rotation from that which determined the original distri- 

 bution of the component matter.'' 



The next branch to which the attention of geologists is called may 

 be termed, according to the author, the true dynamics of geology, 

 with far more justice than that appellation has been applied to other 

 branches of our science. " I would so denominate," he observe*, 

 " the general consideration of the forces which appear to have been 

 the agents in dislocating and elevating our strata ; whether in the 

 earlier geological disturbances, or in the actual phamomena of volca- 

 noes and earthquakes." After noticing the contributions to this de- 

 partment by Von Buch and Elie de Beaumont, and anticipating the 

 conclusions which may be arrived at from the future extension of phy- 

 sical geography and the geology of mountain chains, Mr. C. proceeds : 

 •' There is one source o! analogy which has always appeared to me as 



