438 THE CLIMATE OF THE PLEISTOCENE EPOCH. [Aug. I9OI. 



known temperature at the latter place during February being 52'^, 

 and the average maximum 38°. 



The explanation of these facts is not far to seek. In fig. 11 

 (p. 437), the isobaric chart for February 7th, 1899, is seen an 

 example of the meteorological conditions of the period in question, 

 which shows that the severity of the winter in North America and 

 its excessive mildness in Europe were alike due to the existence of 

 strongly-marked cyclonic conditions in the North Atlantic. Cold 

 winds were constantly pouring over the western continent from the 

 frozen regions of the north, while southerly winds, strictly comple- 

 mentary to them, were flooding Europe with heated air from the 

 subtropical zone.^ 



Under the meteorological conditions now prevalent (fig. 4, p. 414), 

 the average winter climate of the north-eastern part of the American 

 continent must generally be colder than that of North-western 

 Europe at the same latitude ; but the facts just stated seem to 

 indicate that weather unusually mild in the latter may be the 

 necessary accompaniment, and possibly the measure, of extreme cold 

 in the former. 



On the other hand, it is not difficult to understand that the 

 existence of an ice- sheet on the eastern side of the Atlantic may 

 not only have been coincident with, bat possibly even the cause of, 

 an amelioration of the winter climate of Labrador and New England. 

 "When, in winter, Greenland ynd Scandinavia are anticyclonic at the 

 same time, and the high-pressure system of North America shifts 

 westward, the North Atlantic depression moves westward with it 

 towards the American coast, and when the latter lies sufficiently far 

 south as in fig. 12 (p. 439), the isobaric chart for February 28th, 1886, 

 south-easterly winds are experienced in Labrador. The temperature 

 of the latter region during winter varies greatly from day to day. 

 If the winds blow from Greenland or the Polar regions the 

 weather is very cold, but when they veer to the south or south- 

 east the thermometer rises rapidly. On the day just named, the 

 British Isles, Greenland, and Scandinavia being anticyclonic, a 

 low-pressure area lay in the North Atlantic, near Newfoundland, 

 having a south-easterly and north-westerly alignment. The mild 

 winds arising therefrom caused the temperature of the north-western 

 coast of Labrador to rise to 32° Fahr., 63° higher than that registered 

 at the same spot three days previously, and 42° above the average for 

 the month of February.^ In Norway and the Gulf of Bothnia at the 

 same time the theroaometer stood 36° Fahr. lower than in Labrador, 

 although statistically it should have been 30° higher. Such sudden 



^ A number of charts, illustrative of the facts here stated, were exhibited by 

 the Meteorological Council at the E-oyal Society's soiree in May, 1900, and the 

 subject was further dealt with by Oapt. Campbell-Hepworth, of the Meteoro- 

 logical Office, at the Bradford meeting of the British Association in the same 

 year ; see Brit. Assoc. Rep. p. 651. 



^ In the ' Wetterkarten ' we find the following morning temperatures oa the 

 coast of Labrador :— Feb. 25th, 1886, -34° C.= -29° Fahr. ; 

 Feb. 28th. 1886, 0° C.= +32° Fahr. 



