Mabch 1, 1918] 



SCIENCE 



219 



slow-moving glacier, and a glacier is dry when 

 it is cold. Likewise a wet glacier moves 

 rapidly, and a wet glacier is comparatively 

 warm. It may well happen that a slight rise 

 in temperature would cause a forward move- 

 ment of the ice edge and a slight fall in temp- 

 erature a regressive movement. Again, heavy 

 snowfall results in rapid accumulation of ice 

 and is followed by an acceleration in the for- 

 ward or outward push of the ice mass, while a 

 lessened precipitation must result in slower 

 movement and decrease in volume. Possibly, 

 the present retreat of the Antarctic ice is due 

 to a progressive desiccation of Antarctic cli- 

 mate. Temperature is by no means the only, 

 nor necessarily the determining, factor. 



At the same time, it is doubtless true that 

 the climate of the globe is now warmer than 

 it was during the episodes of extensive glacia- 

 tion characterizing the Pleistocene Ice Age, 

 which by the way, was equalled in the magni- 

 tude of its ice sheets by at least one earlier 

 glacial period, that of late Paleozoic time. 

 Moreover, from the geological point of view 

 the present world-climate, with its polar re- 

 frigeration and marked climatic zones, is ab- 

 normal; the earth has oflfered a much more 

 congenial environment than this throughout 

 the greater part of its recorded history. But 

 the data are not now sufficient to point clearly 

 toward a swift and steady replacement of the 

 present semi-glacial temperatures by those of 

 normal and more hospitable range. 



Placing the present moment in earth his- 

 tory in its true i)erspective with relation to 

 the preceding geologic incidents, several alter- 

 natives arise concerning what will be dis- 

 closed on the geologic morrow. During Qua- 

 ternary time oscillations in climate are re- 

 corded by at least four episodes of glaciation 

 separated by intervals of partial or complete 

 dcglaciation. The last great swing of the cli- 

 matic pendulum reached its farthest limit in 

 the direction of refrigeration about thirty 

 thousand years ago. It is possible that the 

 return oscillation will carry the weather con- 

 ditions back to those of the normal, ice-free, 

 geologic period, and Quaternary glaciation will 

 be a thing of the past. On the other hand. 



it is just as likely that the backward rush of 

 the pendulum is now retarding and that soon 

 it will be poised for another sweep in the op- 

 posite direction to bury middle latitudes be- 

 neath the weight of ice sheets of a new glacial 

 stage. In that case we are to-day not in a 

 post-glacial but an inter-glacial time such as 

 that enjoyed by the men of Neanderthal, when 

 osage oranges and paw paws flourished north 

 of Lake Ontario and figs grew in the Kootenay 

 Valley. 



It is unfortunate that no certain selection 

 may be made from tliese alternatives of the 

 one which is imminent, for the question is one 

 of more than academic interest. Legislation 

 which is forward-looking, far-reaching plans 

 for racial progress, promotion of economic 

 welfare, all must be radically influenced by the 

 knowledge — if we had it — that in ten thousand 

 years the Barren Lands of the north could 

 support a population of fifty to the square 

 mile, or that in a similar interval the avail- 

 able farm lands of the globe will be reduced 

 to half their present area. 



The key which will unlock the mystery of 

 the major climatic trend of the present time 

 is not to be found in observations upon the 

 terminal position of ice sheet or glacier, un- 

 less those observations are extended over cen- 

 turies. It is rather to be sought in the deter- 

 mination of the influence which the combus- 

 tion of coal in this industrial age is exerting 

 upon the carbonic-acid content of the air, and 

 of the headway which the warm (though un- 

 usually salt and therefore heav^) water of the 

 Mediterranean Sea is making as it creeps 

 outward through the Straits of Gibraltar down 

 the sloping floor of the Atlantic ocean and 

 spreads poleward beneath the cold but fresher 

 water of the deep sea. 



KmxLEY F. Mather 



Queen's University, 

 Kingston, Canada 



labeling of microscopical slides in 

 staining technique 



There seems to be distinct need of a satis- 

 factory method of temporarily labeling micro- 

 scopical slides destined for the staining, wash- 



