448 



MR. F. W. HAEMEE ON THE 



[Aug. 1901, 



autumn, as we have seen it does during winter and spring, the 

 variations being coincident with changes of wind.^ 



It seems therefore to be the influence of the warm winds prevailing 

 intermittently during the summer that now prevents the permanent 

 accumulation of ice in this region : their character being due, so far 

 as they blow from the land an^ from the south, to the heated state 

 of Korth America at that season. 



When once, however, in consequence of the increasing cold, an 

 i-ce- sheet had begun to establish itself in North America, the region 

 covered by it would have been protected from such winds. Being 

 anticyclonic, the air would have tended to move outward from it in 

 all directions, as Nansen says is now the case in Greenland.^ Cold 

 northerly winds would have been prevalent over Labrador and 

 Hudson Bay at all seasons, and the summer-climate of those regions 

 being changed, the causes which now prevent the formation there 

 of a permanent ice-sheet would have been removed. 



Under such circumstances, I think, the ice might have gradually 

 crept southward. Moreover, as it did so, the storm-tracks would 

 also have shifted in the same direction. At present, the region 

 between the Great Lakes and Newfoundland is one of much atmo- 

 spheric disturbance, and it is to the cyclonic storms that are there 

 frequent that the variable climate of Labrador is largely due. As 

 anticyclonic conditions established themselves, more uniform climatic 

 conditions would have prevailed. Jn this way, the accumulation of 

 the ice might have been self-accelerating. ^ 



In figs. 18 & 20 (pp. 452 & 456) I have endeavoured to reproduce 

 the arrangement of areas of high and low pressure which may 

 bave been prevalent in winter and summer during the maximum 

 glaciation of North America. Eor the purposes of comparison I 

 have given also (figs. 17 & 19, pp. 450 & 454) statistical isobaric 

 charts of the Northern IIemisj)here for January and July, constructed 

 from those in Bartholomew's ' Atlas of Meteorologj" '.^ I have not, 

 however, adopted Mercator's projection (as in figs. 4 & 5, pp. 414 & 



^ The following changes in temperature and in the direction of the wind 

 (2 P.M. local time) took place, for example, in the summer of 1882, at a station 

 in Hudson Strait, on the northern coast of Labrador : — 



Temp. 

 June 4th 59° Eahr. 



5th., 



11th 



12th 



14th 



17th 



20th 



37 

 55 

 37 

 50 

 58 

 34 



Wind. 

 S.W. 

 N.E. 

 S.W. 

 N.E. 

 W. 



s. 



N.E. 



Tewp. Wind. 



June 23rd 6S° Fahr. S.W. 



25th 72 W. 



27th .53 N.E. 



28th 75 S.W. 



JulvSrd 53 IS.W. 



' 8th 47 N.W. 



[From the synchronous weather-charts of the North Atlantic, published under 

 the authority of the Meteorological Coimcil.] 



2 'The First Crossing of Greenland ' vol. ii (1890) p. 496. 



^ That the growth of an ice-sheet, when once established, would be self- 

 accelerating, was shown by James Croll in ' Climate & Time ' 1875, p. 74 ; and 

 also by Dr. A. R. Wallace in 'Island Life' 2nd ed. (1892) p. 151, by Prof. 

 Chamberlin in Journ. Geol. Chicago, vol. vii (1899) p. 675, and others. 



* In summer the isobars of 2990 inches seem rather to group themselves 

 with the high-pressure centres, that of the Polar regions forming a distinct anti- 

 cyclone, and I have so shown it in figs. 19, 20, & 22 (pp. 454, 456, & 460). 



