754 REPORT— 1900. 



times. Oceanic winds, •with copious rainfall, may have prevailed in regions now 

 arid and mild winters where they are now excessively severe. Such cases of 

 anomalous climate as those of the pluvial conditions of the Sahara, and of Arabia 

 and Persia, during the Pleistocene era, may be satisfactorily explained by the changes 

 in the relative positions of cyclonic and auticyclonic systems, which were caused by 

 the o-radual growth and disappearance of the great ice-sheets, as may be the 

 alternate humidity and desiccation of the great basin of Nevada, the former 

 existence of the mammoth on the shores of the Polar Sea, &c. 



It is difficult, however, to restore hypothetically the meteorological conditions 

 of the Pleistocene epoch, on the theory that the maximum glaciation of the eastern 

 and western continents was contemporaneous. At present, the influence of the 

 Gulf Stream and the south-west winds caused by the Icelandic cyclone carries in 

 ■winter a comparatively warm climate, and low pressures, northwards into the Arctic 

 Circle but no permanent ice-sheet could have existed in Great Britain under such 

 circumstances. In the opinion of Professor Jas. Geikie and of Dr. Buchan, the polar 

 basin was filled with ice, and therefore permanently anticyclonic, during the Glacial 

 epoch. Cyclones and anticyclones in regions more or less contiguous are, however, 

 necessarily complementary, in order that the vertical circulation of the atmosphere 

 may be maintained. The existence of an enormous polar anticyclone, extending 

 southwards over a great portion of Europe and North America, would have 

 involved also that of a cyclonic system of corresponding importance in the North 

 Atlantic, a region which must have been at all seasons warmer than thosecovered 

 with ice. If Europe and North America were glaciated at the same time, the 

 Icelandic cyclone, which now lies (statistically) in winter near to the south-east 

 coast of Greenland, would have been forced to the south ; but the further south it 

 went the warmer would have been the southerly winds which blew east of its centre 

 towards Great Britain and Western Europe. Conditions similar to those which 

 may have prevailed during the Glacial period occurred during the early part of 

 1899 for information as to which the author desires to acknowledge his indebted- 

 ness to Mr. W. N. Shaw, F.R.S., of the Meteorological Office. At that time a 

 great low- pressure system, which sometimes extended from Europe to America, and 

 from Iceland to the Canary Islands, occupied the North Atlantic. Vast volumes of 

 cold air were consequently poured over North America, and Western Europe was 

 Hooded by warm aerial currents from the sub-tropical zone. At the beginning of 

 February, temperatures of from -40° F. to -60° F. were commonly registered in 

 different parts of North America ; while at the same time the thermometer rose 

 in London to 66° F., in Liege to 70° F., and in Davos to 62° F., the average 

 maximum for that month at the latter place being 38° F. These coincident varia- 

 tions in the temporary climate of the northern hemisphere are directly traceable to 



the same cause. . , • , 



No meteorological difficulties arise if we adopt the hypothesis that glacial and 

 intero'lacial periods alternated in the eastern and western continents. If the ice- 

 cap extended from Greenland to Scandinavia, the North Atlantic cyclone would 

 have been forced to the south-west, towards the American coast, producing warm 

 south-east winds over Labrador; if, on the contrary, it stretched from Greenland 

 to North America, the cyclone would have been driven in the direction of Europe, 

 causing mild weather in "the latter, as in the case just given. 



Such a view aflbrds a simpler explanation of the geological facts than those 

 usually adopted. Instead of supposing that the climatic changes of the Great Ice 

 ao-e several times recurrent at intervals of a few thousand years only, were due to 

 astronomical causes, it is here suggested that the climate of the Pleistocene 

 epoch being uniformly colder than that of our own era, conditions of comparative 

 warmth oi"cold may have been local, as they now are, affecting the great conti- 

 nental areas at different periods. 



.3. Notes on some Redent Excavations in the Glacial Drift in Bradford. 

 By Jas. Monckman, D.Sc. 



The stream that flows through the Bradford Valley rises on the hills above 

 Thornton and flows in an easterly direction to the centre ot the__ town, where it 

 turns at right angles towards the"^ north and falls into the Aire at bhipley. 



