I think I have got quite matter enough for one paper, but I should like to have the metal if only in sufficient quantity to oxidize up to V₂O₅ and determine the increase. Everything can be very nicely used, and all fits in well; but, of course, such a first paper must in some points be imperfect. I think it is perhaps best that ⸺ should give the lectures, as I am sure to want you in London several Saturdays—otherwise I should have been very glad for you to have taken the course. You will be back on Saturday, October 5th, I suppose. We must re-calculate all the analyses with the exact atomic weight. This can soon be done, and I should like to get this first part off my hands before long. I hope you are enjoying this splendid autumn weather. … As regards the blue oxide got by gradual oxidation of V₂O₃ (suboxide) we have analyses proving it to be V₂O₄—by oxidation. It is very possible that the further increase in weight is due to the hydration of this oxide. We must wait until the green substance remains constant, and we must then determine the water and the V₂O₅. Roscoe’s first memoir on the subject was read to the Royal Society on December 19, 1867, and was made the Bakerian Lecture of that session.[17] On February 14, 1868, he gave a Friday evening discourse at the Royal Institution “On Vanadium, one of the Trivalent Groups of Elements,” when the writer acted as his lecture-assistant. Having arranged the experimental illustrations, the assistant spent a spare half-hour in wandering through the old laboratories in the cellars of the Institution, sacred to the genius and labours of Davy and Faraday. In looking over some specimens in a cupboard he came upon a small bottle containing ammonium vanadate, labelled “Sent to me by Berzelius. 1831,” and on it Faraday’s well-known monogram by way of signature. A portion of the substance was afterwards placed at Roscoe’s disposal by the late Sir Edward Frankland, at the time Fullerian Professor of Chemistry. On examination it was found to contain considerable quantities of phosphoric acid, thus serving to indicate the probable cause of the discrepancy between the numbers obtained by Berzelius and Roscoe in the course of the atomic weight determinations. It had been observed that the presence of even traces of phosphorus prevents the complete reduction in hydrogen of the vanadium pentoxide to vanadous oxide. Some little time after the appearance of the first memoir on vanadium, the writer proceeded to Heidelberg to study under Bunsen, to whom at that time practically all Roscoe’s senior students who were in a position to go to Germany were sent. It had been reported in a French periodical on popular science that Roscoe had been awarded the Copley medal for his work on vanadium, and of course his former assistant had hastened to congratulate him on that event.