432 CAUSES OF THE VARIETIES 



The causes which operate on the bodies of living ani- 

 mals, either modify the individual, or alter the offspring. 

 The former are of great importance in the history of animals, 

 and produce considerable alterations in individuals ; but the 

 latter are the most powerful, as they affect the species, and 

 cause the diversities of race. Great influence has at all 

 times been ascribed to climate, which, indeed, has been com- 

 monly, but very loosely and indefinitely represented as the 

 cause of most important modifications in the human subject 

 and in other animals. Differences of colour, stature, hair, 

 features, and those of moral and intellectual character, have 

 been alike referred to the action of this mysterious cause ; 

 without any attempt to shew which of the circumstances in 

 the numerous assemblage comprehended under the word 

 'climate' produces the effect in question, or any indication of 

 the mode in which the point is accomplished. That the 

 constitution of the atmosphere varies in respect to light and 

 heat, moisture and electricity ; and that these variations, 

 with those of elevation, soil, winds, vegetable productions, 

 will operate decidedly on individuals, I do not mean to deny. 

 While, however, we have no precise information on the 

 kind or degree of influence attributable to such causes, we 

 have abundance of proof that they are entirely inadequate 

 to account for the differences between the various races of 

 men. I shall state one or two changes, which seem fairly 

 referable to climate. 



The whitening (blanching or etiolation) of vegetables, 

 when the sun's rays are excluded, demonstrates the influ- 

 ence of those rays on vegetable colours. Nor is the effect 

 merely superficial : it extends to the texture of the plant, to 

 the taste and other properties of its juices. Men much ex- 

 posed to the sun and air, as peasants and sailors, acquire a 

 deeper tint of colour than those who are more covered ; and 

 the tanning of the skin by the summer sun, in parts of the 

 body exposed to it, as the face and hands, is a phenomenon 

 completely analogous. The ruddy and tawny hues of those 

 who live in the country, particularly of labourers in the 

 open air, and the pale sallow countenances of the inhabitants 



