I didn’t arrive in London until the 20th of September. On my arrival I found that Count Rumford had altered his plans of absence, and had left London on that very day for the Continent, purposing to return in about two months. He is now at Paris, and in about a fortnight we expect him here. * * * * * I yesterday ascertained rather an important fact; namely, that a galvanic battery may be constructed _without any metallic substance_. By means of ten pieces of well-burnt charcoal, nitrous acid, and water, arranged alternately in wine-glasses, I produced all the effects usually obtained from zinc, silver, and water. The Bakerian lecture[34] by Dr. Young, our Lecturer on Natural Philosophy, is now reading before the Royal Society. He attempts to revive the doctrine of Huygens and Euler, that light depends upon undulations of an ethereal medium. His proofs (_i.e._ his presumptive proofs) are drawn from some strong and curious analogies he has discovered between light and sound. * * * * * You should fix your permanent residence in London, where alone you can do what you ought--instruct and delight numbers of improved men. I am, my Friend, yours with unfeigned esteem and respect, HUMPHRY DAVY. On January 5, 1802, a syllabus of Davy’s course of lectures on Chemistry was printed at the press of the Royal Institution. He wrote for it the following advertisement: It is generally admitted that the best method of teaching the sciences is to begin with simple facts, and gradually to proceed from them to the more complicated phenomena. In the following pages, which contain the outlines of a course of lectures on Chemistry, an attempt has been made to employ such a method. Hence the abstruse doctrines concerning the imponderable fluids have been separated from the history of simple chemical action, and the applications of the science from the science itself. The classification of substances adopted is founded rather upon facts than analogies, and in consequence certain bodies have been placed among the simple principles which, from their resemblance to other bodies of known composition, have been generally arranged in the class of compounds. This is an imperfection, but on the principles assumed it could not easily be avoided. And it will be fortunate for the author if a discerning public should not discover many more important imperfections. Part I. ‘The Chemistry of Ponderable Substances.’ Part II. ‘The Chemistry of Imponderable Substances.’ Div. 1, of Heat or Caloric; Div. 2, of Light; Div. 3, of the Electric Influence; Div. 4, of Galvanism.