and frost occurred when the ground was a few degrees colder than the air above. But they thought the cold was caused by the dew and frost, not the other way around. In the autumn of 1811 Wells took some measurements and soon came to doubt his old idea. He began serious experiments soon after and published the results in August 1814. He compared the formation of dew under varying conditions of material, location, temperature, humidity, weather, cloud cover, season, and time of day. Wells concluded that dew is a condensation of water vapor in the air caused by just the right combination of conditions involving especially temperature, temperature change, and heat conductivity of materials. Wells' inquiry into the nature of dew were widely cited in the 1830s as an outstanding example of inductive scientific inquiry. Sir John Herschel used it as the primary illustration in his Discourse on the study of Natural Philosophy, calling the theory, "one of the most beautiful specimens we can call to mind of inductive experimental enquiry lying within a moderate compass." In 1836, the Encyclopedia Metropolitana reported, "We know of no work in our day which has been more universally admired than the Treatise of Dr. Wells, certainly none that practically exemplifies in a purer and better form the admirable inductive system which it was the object of Bacon to teach." John Tyndall and William Whewell praised it similarly. Publications Wells W.C. 1814. An essay on dew. Taylor & Hessay, London. [The basis of his Rumford Medal] Wells W.C. 1818. Two essays: upon a single vision with two eyes, the other on dew. Constable, London. This contains an appendix titled An account of a female of the white race of mankind, part of whose skin resembles that of a negro, with some observations on the cause of the differences in colour and form between the white and negro races of man. [It is this last part which contains the idea of natural selection. The book, which concludes with a memoir of his life, written by himself, contains the material which he had designated for publication before his death; apparently there was other material destroyed on his instructions]. Most of his writings on medical subjects are contained in the second and third volumes of the Transactions of a Society for the Promotion of Medical and Chirurgical Knowledge 1811-12: Observations on Erysipelas. An instance of an