Pearsall has been working, as you know, on red manganese solutions. He has not proved, but he makes out a strong case for the opinion, that they owe their colour and other properties to manganesic acid. This paper will be in the next number of the Journal. With regard to the gramme, wine-pint, etc., etc., in the manipulation I had great trouble about them, for I could find no agreement, and at last resolved to take certain conclusions from Capt. Kater’s paper and the Act of Parliament, and calculate the rest. I think I took the data at page 67, paragraph 119, as the data, but am not sure, and cannot go over them again. My memory gets worse and worse daily. I will not, therefore, say I have not received your Pharmacopœia--that of 1824 is what I have at hand and use. I am not aware of any other. I have sent a paper to the R. S., but not chemical. It is on sound, etc., etc. If they print it, of course you will have a copy in due time. I am, my dear Phillips, Most faithfully and sincerely yours, M. FARADAY. Is it right to ask what has become of Badams? I suppose he is, of course, a defaulter at the R. S. [Sidenote: SACRIFICES FOR SCIENCE.] This sacrifice for science was not small. He had made £1,000 in 1830 out of these professional occupations, and in 1831 would have made more but for his own decision. In 1832 some Excise work that he had retained brought him in £155 9s.; but in no subsequent year did it bring in so much. He might easily have made £5,000 a year had he chosen to cultivate the professional connection thus formed; and as he continued, with little intermission, in activity till 1860, he might have died a wealthy man. But he chose otherwise; and his first reward came in the autumn of 1831, in the great discovery of magneto-electric currents--the principle upon which all our modern dynamos and transformers are based, the foundation of all the electric lighting and electric transmission of power. From this work he went on to a research on the identity of all the kinds of electricity, until then supposed to be of separate sorts, and from this to electro-chemical work of the very highest value. Of all these investigations some account will be found in the chapters which follow.