The Climate of Great Britain. 119 



A tendency to break up into two curves is exhibited in 

 the isotheral, even more markedly than in the two other 

 curves. But singularly enough, here, where one would expect 

 more certain information of the existence of poles of cold, 

 since so much more of the northern hemisphere can be 

 traversed in summer than in winter, we have no satisfactory 

 evidence. In fact, the irregular curve marked in near the 

 pole in Fig. 2 is the most northerly isotheral yet determined.. 

 The temperature corresponding to this isotheral is 36° Fahren- 

 heit, or four degrees above freezing. From a consideration of 

 the form -variations of the isotherals as they travel northwards, 

 I have been led to the opinion that there exist three poles of 

 summer cold, and that these fall not very far from the posi- 

 tions indicated by the small dark circles in Fig. 2, 



From the direction of the isotheral line through London^ 

 it is evident that along the southern coast of England the heat 

 of summer* is greater than in any other part of the British 

 Isles. On the other hand, the northern parts of Scotland, 

 which we have seen, enjoy a winter climate fully as warm as 

 that of London, have a much cooler summer climate. The 

 south-western parts of Ireland exhibit a change even more 

 remarkable. For whereas the winter climate in these parts is 

 the same as that of Persia, the summer climate is the same as 

 that of the very portion of Siberia in which (most probably) the 

 greatest cold ever observable in our northern hemisphere is 

 experienced in winter. The summer of the Orkney Islands, 

 again, is no warmer than that of the southern parts of Iceland. 



It appears, then, that the inhabitants of England enjoy 

 three notable advantages as respects climate. First, a higher 

 mean annual temperature than that of any other country so 

 far from the equator ; secondly, a moderate degree of cold in 

 winter; and, lastly, a moderate degree of heat in summer. 

 The last two advantages resolve themselves into one, viz., 

 small range of temperature throughout the year. Our range of 

 climate is from about 36° in winter to 62 i° in summer, or in 

 all, 26£° Fahrenheit. Compare with this the climate of the 

 country near Lake Winnipeg, with a winter cold of 4° below 

 zero, and a summer heat scarcely inferior to that of London ; 

 so that the range of climate is no less than (55°. Yet more 

 remarkable is the variation of climate in parts of Siberia, near 

 Yakutsk ; here the range is from — 4u° in winter to 62° in 

 summer — a variation of 102°, or four times the 'variation of 

 our London climate. Other parts of the British Isles have, 

 however, a yet smaller range even than that of London. 

 Thus in the south-western parts of Ireland, and in the Orkney 

 Isles, the variation is less than 19°. 



Nor is it difficult to assign sufficient reasons for the mild- 



