4G6 OX THE SOURCES OF HEAT WHICH INFLUENCE CLIMATE. 



We have now seen that the heat which influences our climates may be traced 

 to the four following sources : 



1. The calorific power of the solar rays, which are well known to vary directly 

 with the latitude. 



2. The temperature of the planetary spaces, which apply equally to every 

 portion of the earth's surface. 



3. The heat of the central mass of our earth. 



4. The caloric changed by every variation from one state to another. 



Of these sources of heat the two first govern, for the most part, our various 

 climates; besides their influence, it is scarcely necessary to add that other cir- 

 cumstances have much effect on climate, as, for example, the hygrometric state 

 of the atmosphere, the proximity of other continents, the prevailing winds, the 

 character of the soil, and several others that form of themselves a distinct branch 

 of inquiry, but which it is not necessary for me now to enter upon. Their effects 

 are at once made obvious by referring to the isothermal lines, or lines of equal 

 temperature traced by Humboldt, which can be shewn to deviate much from the 

 parallels of latitude. 



In Europe the position of places with the same annual heat does not differ more 

 than eight or nine degrees, but the difference of those having the same winter 

 temperature is not less than 18 or 19 degrees. The winter of Scotland is as mild 

 as Milan in North Italy. Ireland is remarkable for mild winters and cold sum- 

 mers. The mean temperature in Hungary for the month of August is 71 -^ 

 degrees ; while in Dublin for the same month it is only 60| degrees. New York 

 has the summer of Rome and the winter of Copenhagen. Quebec has the 

 summer of Paris and the winter of St. Petersburg. In the same manner, at Pekin, 

 which has the mean temperature of Britain, the heat of summer is greater than at 

 Grand Cairo in Egypt ; and the cold in winter as severe as at Upsal, in Sweden. 



These inequalities are due to a complex set of phenomena which regulates the 

 machinery of climates. It is uncertain if we shall ever be permitted to view 

 this machinery ; but there can be little doubt that we should there see the same 

 system of compensation for apparent irregularities as the imperishable labours of 

 Newton and La Place have shewn to us in the movements of the heavenly 

 bodies ; and which there are ample reasons for our supposing to extend to all the 

 other works of Nature. 



[The object of The Naturalist, as expressed in the title-page, and as carried 

 out in the body of the work, is to illustrate the animal, vegetable, and mineral 

 kingdoms. But we feel assured that neither our readers nor ourselves can object 

 to an occasional digression into collateral branches of Natural Science. Or did 

 such a scruple exist, surely it would altogether vanish on perusal of any paper so 

 interesting and so ably written as the preceding. — Ed.] 



