II 



BULLETIN OF THE NATURAL HISTORY SOCIETY. 



posit. The interlayers must have 

 been caused by an intermittingly 

 warmer climate. The peat deposit 

 shows that a considerable period of 

 warm weather must have intervened, 

 for such an accumulation to accrue, 

 as that found in this particular stra- 

 tum. 



Where sand or gravel is found, 

 it is probably consequent upon the de- 

 pression of the land to below the 

 point of submergence; this portion be- 

 coming subsequently re-elevated and 

 subject to re-glaciation. The great 

 weight and power of the moving ice 

 has in some places crumpled the 

 shales and other rocks over which it 

 passed, in the line of their lam'nation. 

 The Glacial Clays partake largely af- 

 ter the nearest rocks over which they 

 passed, with regard to color. 



The geographical extent of the ice 

 in the northern hemisphere was, 

 roughly speaking, bounded by the 50th 

 degree north latitude in Europe, 

 w^hilst in America it was bounded by 

 parallel 39. It England It does not 

 seem to have reached fur+her south 

 to any extent, than tbe n rth of the 

 Thames Basin. During this time the 

 British Isles were united wi'h the 

 European Continent by a vast ice 

 ih€et, the whole of the land surface, 

 both in Europe and America, being 

 then, probably, of considerably g eater 

 elevation than at present. South of 

 parallel 50 i,i Europe, immense glaciers 

 would be produced on the Alps, Car- 

 pathians, and Pyrenees. In fact, the 

 present Swiss and Pyrenean glaciers 

 are the pigmy remains of once im- 

 rheasurably larger ice fields. In Asia 

 we flpd proofs that far larger glaciers 

 • exieted'ln the Himalaya Range than 

 those o^t-Kpv'Ccgsent day, '.occupyijig 

 the 'fS^tlfl^i'^Sijfi. evert. d6:iv.n*-+o-with"- 

 in som^jrj^iOO-" feet.; of, thfe.^'sea; ..4'evel. 

 Similar evidence^if Of large glaciers in 

 New Zealand are obtained, whilst 

 traces of proof of firmer glacial 

 action are found in ^PO.th..,A^&tj^lia 

 and South America. ^ .^\;ffi9iS^*•>^••• 



Geological exploration ' Has, as 

 yet, been confined . ta.- so • com- 



paratively few regions, that any- 

 thing like a complete knowledge 

 oT the range of ice during the glacial 

 age, has not t,een attained. One fact 

 should be very clearly borne in mind, 

 that the occupation of a certain area 

 by ice does not necessarily imply that 

 that pai-ticular district has a so much 

 lower mean temperature, than other 

 places in the saine latitude where no 

 ice exists. Through local causes, the 

 precipitation of moisture in the form 

 of snow is so much greater in some 

 d'stricts than in others, that the sup- 

 ply so far exceeds the melting power 

 of the atmosphere as to cause such 

 an accumulation that a glacier is the 

 result. We know that there are dis- 

 tricts where moisture seldom or never 

 falls, in cold, as well as in hot dis- 

 tricts. Take Siberia as an instance. 

 If any very large quantity of snow 

 fell over that immense territory, 

 it would become one huge glac- 

 ier, and be totally uninhabitable. 

 Most certainly would this be the case 

 north of parallel 60; yet at Yakutsk it 

 is possible to live, notwithstanding the 

 fact that the ground is permanently 

 frozen to a depth of 700 feet. 



Some geologists consider that 

 there has been a succession 

 of Glacial Ages, ranging from 

 Cumbrian Times, onward through 

 the Devonian, New Red Sandstone, 

 Lias, and Cretaceons, to the Pleisto- 

 cene. The evidences, however, are 

 not definite enough to be considered 

 conclusive; although Sir A. C. Ram- 

 sey and other writers, hold the opinion 

 that there are traces of glacial action, 

 in some of the deposits of those ages. 



The ice age which wrought upon so 

 considrable a portion of the earth's 

 syi^ce, such" frrfportant and remark- 

 a^^ changes, that often the entire 

 contour was altered, took place at a 

 comparatively recent date. Various 

 causes have been assigned for the 

 lowered temperature of the trlobe at 

 that time. In many places the land 

 was much higher than now, and high 

 ridges of land would act as cond ^n^ors 

 of the moisture, causing it to fall as 



