Chap. XXXII.] CLIMATE. 541 



It will also be instructive to compare the mean temperature of 

 the four seasons in both places. 



Paris. London. 



Fahr. Fahr. 



Mean TcmiTcraturc, Spring 50-0 . . . 49-0 



Ruinnicr G4-8 . . . G2-5 



„ Autuiiiii 52-0 . . . 51-0 



Winter 3'J-5 . . . 39-0 



It must, however, be borne in mind that in the suburbs of 

 London the mean temperature is 2^ F. below that of the city, and 

 that on winter nights, when Jack Frost is striving his hardest to 

 destroy all the vegetation within his reach, there is often as 

 much as 4^ F. between the thermometers of the city and the 

 suburbs. The cause of this variation is twofold. In the summer 

 a large quantity of heat is radiated by the masses of brickwork in 

 the city, to say nothing of the amount of solar heat absorbed by 

 day and given off again during the night ; while in the winter 

 the city is obviously warmer than the suburbs during both day 

 and night, on account of the extra heat caused by the numerous 

 fires, both industrial and domestic. Paris, as a city, being under 

 precisely similar conditions, we may feel safe in assuming that 

 the same difference exists between the mean temperature of the 

 Observatory and Montreuil as between that of Somerset House 

 and Tottenham for instance. Luke Howard, one of our most 

 acute British meteorologists, on the strength of many thousands 

 of observations made at Plaistow, Stratford, and Tottenham, gives 

 the difference between the mean temperature of London and the 

 country as 2^ F. exactly, and a careful examination of his data 

 has proved his figures to be correct within a fraction. This 

 difference sinks to less than half a degree in spring ; it increases 

 in summer and autumn, and often rises on winter nights to as 

 much as 4i" F. It is a singular fact that towards the end of 

 spring, when the fires are being discontinued, and the sun has 

 not yet reached his full power, it sometimes happens that the day 

 temperature is somewhat greater in the country. This is 

 doubtless to be attributed to the veil of smoke and cloud that is 

 hanging over the metropolis which intercepts the action of the 

 sun. The effects of the higher mean winter-temperature in the 

 city are singularly apparent in the earlier budding and blooming 

 of the trees, which frequently begin their spring life several days 



