V 



A. Vcmghan — Corrugation of the EarWs Surface. 263 



flood, mentioned by Florus as the cause of the migration of the 

 Cimbri and the Teutones. The occurrence of the remains of a boat 

 in the 20-foot beach on the Clyde points to one of these movements 

 at least having been much later than the diluvial movement which 

 destroyed the Mammoth and its companions. Perhaps the deposition 

 of this beach vs^as coincident with the so-called Cimbric flood. 



These are questions, however, which the future must settle ; what 

 we are now chiefly constrained to urge is, that the raised beaches 

 which have been supposed to index immense movements of the 

 earth's crust, up and down, are capable of a much more moderate 

 and much more plausible explanation, namely, that they are neck- 

 laces put about the land by the amorous sea in one of its more ardent 

 moments, and correspond to the line of wreckage in the fields after 

 an inundation. 



VI. ThK CoRRUaATION OP THE EaRTH's SuRFAOE AND VoLOANIO 



Phenomena.' 

 By Arthur Vaughan, B.A., B.Sc. 



IT is important, in the first place, to discuss those facts concerning 

 the Earth which must be taken into account in any attempt to 

 deal satisfactorily with the problem before us. 



To a depth of about 80 feet in Temperate regions, the earth has 

 its temperature determined by the seasons ; being warmed in summer 

 and cooled in winter. Below this average depth the temperature 

 remains constant throughout the year, and shows a steady increase 

 as we go downwards. By observations made in deep borings, it is 

 found that this increase is at the rate of about 1° F. for every 60 feet, 

 and that this law holds true throughout a descent of several hundred 

 feet ; but that the rate of increase diminishes at considerable depths. 

 This increase in temperature with distance from the surface points 

 unmistakably to a large store of heat in the interior of the earth, 

 and the increase in the rate at which temperature diminishes, as we 

 approach the surface, agrees with what we should expect to happen 

 if a large heated mass were allowed to cool ; the nearer the surface 

 the greater would be the rate of loss of heat, and consequently the 

 more rapid the diminution of temperature. 



The next important point to be considered is that, however the 

 rocks near the surface may differ in composition, they are all dis- 

 tinguished by being divided up into larger or smaller portions by 

 joints, bedding-plane, etc. The actual amount of separation caused 

 by this means varies very much with different rocks ; but in so far 

 as it exists must necessarily allow of closer approximation if the 

 rocks ever become subjected to great pressure. That this jointing 

 is sufficient to allow of seasonal expansion is obvious, notwith- 

 standing the fact that the difl'erence between summer and winter 

 temperature in continental regions is often extreme. Again, this 

 division into smaller portions by jointing, etc , remains true at all 



^ The author wishes it to be stated that this article was sent in on March 31st, 

 1894, but has not appeared earlier for want of space. — Edit. Geol. Mag. 



