During 1799, Beddoes and Davy published Contributions to physical and medical knowledge, principally from the west of England and Essays on heat, light, and the combinations of light, with a new theory of respiration. On the generation of oxygen gas, and the causes of the colors of organic beings. Their experimental work was poor, and the publications were harshly criticised. In after years Davy regretted he had ever published these immature hypotheses, which he subsequently designated "the dreams of misemployed genius which the light of experiment and observation has never conducted to truth." These criticisms, however, led Davy to refine and improve his experimental techniques, spending his later time at the institution increasingly in experimentation. 
In December 1799 Davy visited London for the first time and extended his circle of friends. Davy features in the diary of William Godwin, with their first meeting recorded for 4 December 1799.
In 1800, Davy informed Giddy that he had been "repeating the galvanic experiments with success" in the intervals of the experiments on the gases, which "almost incessantly occupied him from January to April." In 1800, Davy published his Researches, Chemical and Philosophical, chiefly concerning Nitrous Oxide and its Respiration, and received a more positive response.