CAMFIELD PLACE, HATFIELD, HERTS, _September 13, 1868_. In the first place let me thank you for your letter and congratulations upon the great French discovery! Many of these Parisian wonders have after all turned out myths—and this last is, I believe, no exception—the expression “Medaille de Copley” is, so far as I am aware, the French (and bad French too!) for the “Bakerian Lecture.” I am, however, none the less obliged to you for your good wishes on this occasion, and for all the valuable help which in many ways you gave me. … Thanks for your news of my dear friend. I have been very remiss in not writing to him. Tell him so, please; and ask him to send me the first proof-sheets of his “Filtration” paper for me to translate; unless, indeed, you do it yourself, as I am sure you can perfectly well. Give B[unsen] my kindest regards, and say that I will write to him soon. Part II of “Researches on Vanadium,” dealing with the chlorides VCl₄, VCl₃, and VCl₂, and metallic vanadium, which he obtained by heating the dichloride in hydrogen, was presented to the Royal Society on June 16, 1869,[18] and his last memoir, treating of the bromides, and of certain of the metallic vanadates, including vanadinite which he prepared artificially, on April 7, 1870.[19] With the mention of a short communication, “On Two New Vanadium Minerals,” to the _Proceedings of the Royal Society_ for 1876,[20] and of a lecture on “Recent Discoveries about Vanadium” at the Royal Institution, the foregoing statement includes all Roscoe’s published contributions to the history of vanadium. As regards original work, he handed over the subject to his senior students, and under his inspiration and direction a considerable number of communications from the Owens College Laboratory were made to the Chemical Society from Crow (1876), Bedson (1876), H. Baker (1878), Kay (1880), Brierley (1886), Hall (1887), and published in the _Transactions of the Chemical Society_. * * * * * Other noteworthy contributions by Roscoe to inorganic chemistry are his study of tungsten compounds, in which he describes for the first time the existence of the pentachloride WCl₅ and the corresponding pentabromide WBr₅,[21] and his discovery of uranium pentachloride, UCl₅.[22] These compounds are of considerable theoretical interest on account of their “anomalous” character. He also discovered columbium trichloride, CbCl₃, which he found to have the remarkable property of decomposing carbon dioxide when heated in that gas with the formation of columbium oxychloride, CbOCl₃, and carbon monoxide—a reaction not exhibited by any other metallic chloride (_Chem. Soc. Abstracts_, 1878, 272), and he determined the vapour densities of the chlorides of lead and thallium which he showed to be normal.[23]