blacks and browns were mixtures of carbonaceous matter with oxides of iron or manganese. The whites were mainly chalk, or occasionally clay; cerusse, or white-lead, was apparently not used. Before leaving Italy he again went to Naples, for the purpose of witnessing Vesuvius in eruption, and on several occasions he was as near the crater as he could get. He left Naples on March 21st, and came home by way of Verona, Innsbruck, Ulm, Stuttgart, Heidelberg, and the Rhine, arriving in London April 23rd, 1815. A few days after his arrival he wrote to his mother:-- “We have had a very agreeable and instructive journey and Lady Davy agrees with me in thinking that England is the only country to _live_ in, however interesting it may be to _see_ other countries. “I yesterday bought a good house in Grosvenor Street, and we shall sit down in this happy land. “I beg you to give my best and kindest love to my sisters, and to remember me with all affection to my aunts.” Faraday was again engaged as assistant in the laboratory of the Royal Institution and superintendent of the apparatus (at a salary of 30s. a week), and was accommodated with apartments at the top of the house. In Dr. Bence Jones’s “Life of Faraday” we have more detailed information concerning this tour, derived from the journal which Faraday kept whilst he was abroad. Faraday describes in considerable detail the life in Paris and the work on Iodine; we have accounts of Chevreul’s laboratory at the Jardin des Plantes, and of Gay Lussac’s lectures at the École Polytechnique; of the work on the torpedo at Genoa; of the combustion of the diamond at the Accademia del Cimento, and a description of the great burning-glass, and how it was actually employed; of the experiments of Morichini on the alleged magnetisation of a needle by the solar rays; of his meeting Volta--“an hale, elderly man, bearing the red ribbon, and very free in conversation”; of the work at Rome on chlorous oxide and iodic acid, and on the pigments employed by the ancients. “The constant presence of Sir Humphry Davy,” wrote Faraday to his friend Abbott, “is a mine inexhaustible of knowledge and improvement.” But he adds: “I have several times been more than half decided to return hastily home; but second thoughts have still induced me to try what the future may produce ... the glorious opportunities I enjoy of improving in the knowledge of chemistry and the sciences continually determine me to finish this voyage with Sir H. D. But if I wish to enjoy these advantages I have to sacrifice much, and though these sacrifices are such as an humble man would not feel, yet I cannot quietly make them.”