CLIMATE. 33 



above that of the whole year ; and the mean of winter 

 as much below ; the mean of autumn being 1° or 

 2° higher, and that of spring 1° or 2° lower than the 

 annual mean. At Penzance there is the nearest ap- 

 proach to equalisation, the means of winter and summer 

 differing only 8° from that of the year. The con- 

 trary holds at London, where the mean of winter is 

 11° below, and that of summer 13° above, the annual 

 mean. At Oxford, these differences are reversed. At 

 Gosport, the summer and winter means respectively are 

 about 11^° distant from that of the year. Northward of 

 lat. 52°, the summer mean is below 60°, unless in very 

 fine seasons, and usually above 57°. Southward of this 

 lat it is from 60° to 63°. The recorded extremes at 

 London in the last forty years are — 6 and -f 94 ; the 

 range of Fahrenheit's thermometer therefore being 100°. 

 I believe the average extremes are about 20° and 85°. 



b. Rain. 



The distribution of heat we have seen to be in accord- 

 ance chiefly with latitude and elevation, modified con- 

 siderably by local or geographical position. The quantity 

 or distribution of rain bears reference principally to the 

 latter condition. The quantity of rain falling in Britain 

 varies much both annually and locally. In general, it 

 may be said that the quantity is greater towards the 

 western coasts, and near the mountain tracts. The usual 

 mode of estimating the quantity of water falling as rain 

 or snow is by the depth of inches, supposing it evenly 

 spread over the surface, and no evaporation. In the fol- 

 lowing table are brought together a number of mean re- 

 sults obtained by the rain-gage; and though some of 

 them may not be very precise, trifling inaccuracies will 

 not materially affect the general means. Some source of 

 fallacy must be conjectured in the estimate for Glasgow. 



c 5 



