ON THE SOURCES OF HEAT WHICH INFLUENCE CLIMATE. 465 



14 If the terrestrial globe and all the bodies which compose the solar system, were 

 placed in an inclosure devoid of all heat, phenomena would be observed entirely 

 contrary to those which we now know to exist. The polar regions would endure 

 an immeasurable cold, and the decrease in the temperature, from the equator to 

 the poles, would be incomparaby more rapid and extensive. 



" Upon the hypothesis of the absolute cold of space, if it is possible to conceive 

 it, all the effects of heat, such as we observe them on the surface of the globe, 

 would be owing to the presence of the sun ; the least variations of distance from 

 that orb would occasion very considerable changes of temperature in the earth. — 

 At the commencement of night the surfaces of bodies would be instantaneously 

 exposed to an infinitely intense cold, and organic bodies would not be able to 

 withstand the equally sudden action of a contrary description, which would take 

 place on the rising of the sun." 



Thus we perceive that this low temperature assigned to the celestial regions 

 through which our planet moves, has a most vigorous effect on the climate at the 

 earth's surface ; its power will be invariable for every point of the globe, whether 

 placed under the torid zone or within the polar circle, whether on a level with 

 the sea or in elevated mountain ranges. 



That the rays from the moon are totally devoid of any calorific effects, seems 

 to have been recently finally set at rest, from experiments made by the beautiful 

 thermo-multiplier of Melloni ; this leads to the conclusion that the surface of that 

 luminary possesses only the temperature of the planetary spaces, and there, in 

 the absence of the solar rays, cold will be experienced of minus 58, Fahrenheit. 

 From this it may be inferred that organic bodies, such as we are acquainted with, 

 cannot exist on the moon's surface. 



Only one other source of heat known to us remains to be spoken of. It is 

 the caloric, either given out or absorbed in every process, whether natural or 

 artificial, which involves change from one state to another. This cause will act 

 on climates generally chiefly through the spontaneous variations in the hygro- 

 metric state of our atmosphere ; and it will be through this indirect channel that 

 the artificial processes of cultivation are capable of improving climate. Other 

 artificial means, derived from the works always carried on in densely-peopled 

 districts, or in cities, modify the temperature to an extent of one or two degrees 

 of Fahrenheit. 



The climate of London is considerably changed through this, the mean annual 

 temperature exceeding that of the surrounding country by half a degree ; the 

 difference would be greater were it not that London, always veiled by smoke 

 from the full power of the sun, has a colder mid-day temperature than its 

 environs, while the nights of mid-winter are nearly four degrees higher than the 

 heat of the surrounding country. 



