published in 1818. This was Two Essays... with some observations on the causes of the differences of colour and form between the white and negro races of men. By the Late W.C. Wells…with a Memoir of his life, written by himself. Wells was clearly interested in how different races might have arisen. After some preliminary remarks on the different races of man, and of the selection of domesticated animals, he observes that: "[What was done for animals artificially] seems to be done with equal efficiency, though more slowly, by nature, in the formation of varieties of mankind, fitted for the country which they inhabit. Of the accidental varieties of man, which would occur among the first scattered inhabitants, some one would be better fitted than the others to bear the diseases of the country. This race would multiply while the others would decrease, and as the darkest would be the best fitted for the [African] climate, at length [they would] become the most prevalent, if not the only race." Charles Darwin and Alfred Russel Wallace were not aware of this work when they published their theory in 1858, but later Darwin acknowledged: "In this paper he [Wells] distinctly recognizes the principle of natural selection, and this is the first recognition which has been indicated; but he applies it only to man, and to certain characters alone. After remarking that negroes and mulattoes enjoy an immunity from certain tropical diseases, he observes, firstly, that all animals tend to vary in some degree, and, secondly, that agriculturalists improve their domesticated animals by selection; and then he adds, but what is done in this latter case by art, seems to be done with equal efficacy, though more slowly, in the formation of varieties of mankind, fitted for the country which they inhabit." Credit for the first appreciation of natural selection could therefore go to Wells rather than to Edward Blyth or Patrick Matthew. The triumph is limited to the extent of being applied only to skin colour, and not, as Darwin and Wallace did, to the whole range of life. A form of the idea had already been set out by an earlier Edinburgh author, James Hutton, but in that case the effect was limited to improvement of varieties rather than the formation of new species. Wells' work on dew In the 1780s, Wells and a few others had the idea that dew