THEORY OF NATURAL SELECTION FORESHADOWED. 181 



science. Before the time of Sir Humphry Davy, also, it 

 was suspected and assumed that the alkalies were com- 

 pound substances containing metallic bases; but it was, 

 not until he applied an extremely powerful voltaic current 

 from the great battery of the Eoyal Institution to 

 those substances, that the hypothesis was proved to 

 be true, and the metals potassium and sodium were first 

 isolated. 



Even Darwin's theory of natural selection was in some 

 degree prelumined in a paper ' On a Woman of the White 

 Eace whose Skin partly resembled that of a Negro,' by Dr. 

 W. C. Wells, read before the Koyal Society as early as the 

 year 1813. He remarks that all animals have a power, to 

 a certain extent, of adapting themselves to altered circum- 

 stances, and are thereby themselves changed ; and that 

 farmers, by subjecting animals to different conditions, and 

 selecting particular animals, improve their stock, and he 

 remarks that what is thus effected by art seems to be 

 done with equal efficiency, though slowly, by nature, in 

 the formation of varieties of mankind fitted for the country 

 which they iohabit. 



Of the accidental varieties of man which would occur 

 amongst the first few and scattered inhabitants of the 

 middle regions of Africa, some one would be better fitted 

 than the others to bear the diseases of the country. This 

 race would consequently multiply, while the others would 

 decrease, not only from their inability to sustain the 

 attacks of disease, but from their incapacity of contending 

 with their more vigorous neighbours. The colour of this 

 vigorous race, I take for granted from what has been 

 already said, would be dark. But the same disposition 

 to form varieties still existing, a darker and a darker race 

 would in the course of time occur ; and as the darkest 

 would be the best fitted for the climate, this would 



