146 CLIMATE. 



The air climate is in fact postponed by so many days ; just as 

 in an apartment some time elapses after the fire is at the hottest 

 before the cold of the walls is reduced enough to allow of the 

 full warming of the air. If instead of taking the register of the 

 daily temperature in the open air, we try it in a large building 

 without fire, we find the climate of the building further post- 

 poned. In York Minster for example, it is found by a series of 

 daily observations continued for three years, that the hottest day 

 is above five weeks after the summer solstice, or a fortnight after 

 the hottest day in the open air ; and the coldest day about five 

 weeks after the winter solstice, or a fortnight after the coldest 

 day in the open air. 



This postponement of the effect of summer and winter in- 

 fluences is still more sensible and regular below the surface of 

 the ground. By many experiments in Scotland, France, Belgium, 

 and Germany, which have been completely studied by Quetelet 

 and Forbes, it is found that the middle of summer and winter, 

 so to speak, occur 



At the surface in July and January ; 



3 feet deep in August and February ; 



12 feet deep in October and April; 



24 feet deep in December and June ; 



And at less than 100 feet in July and January of the 



following year. 



Masses of elevated land, and broad tracts of deep water, affect 

 climate in the same way, by giving out in late autumn and 

 winter some warmth which they had acquired in summer, and 

 on the other hand, by absorbing in spring and early summer a 

 more than fair proportion of the solar heat. Hence one of the 

 advantages to the invalid of a prolonged residence at Scarborough, 

 or in some sheltered Yorkshire dale, till December, January, and 

 even February, have spent their cooling power on the inland 

 surfaces; but for the same reasons the disadvantage of these 

 stations in March, April, and even May. 



But it is not only by prolonging the summer and postponing 



