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cular and gray and so unlike what Brodie' made with greatcare and called the right peroxide, 2 that I doubt it, but I shallknow better when I receive your Instructions. I havc forgottenthe preparation of HO© by the fluor salicic acid — where isit described in French, or where is it? — What strength doyou prepare HO©, strong or dilute? — The peroxide of man-ganese, do you employ the natural or of the artiflcial ? whatis your process of preparation for Solution in A. A. and doyou use it wet or dry?

I have had the paper on reciprocal catalysis (23 June 1858)translated, so have, with the letters etc, obtained possessionof part of your thoughts. But it is the experimental proofsand the racthod of making them perfectly, about which I amanxious and none but the discovering philosopher himself knowshow best to make their value evident. For that reason I desireto work with your tools, and in your way and if the chemical[preparations] you refer to are to be bought in Bälc, in whatyou know to be the right State, send them to me, but if not,do not waste your time personally. I shall prepare them fromyour Instructions.

I had your letters etc by Dr. Bernoulli on the i/th instant.I did not sec bim for he sent them by post and was to leaveLondon the next day. He had been ill and detained in Berlin.But I could not teil when you had written, for your letter hadno date and stränge to say ncither had his, except the Post-mark. Yours by him and mine to you must have passed inthe road.

Kindest remembrances to the houschold from one always

under Obligation to vou and ever vours ,. _

ö M. hARADAY.

1 Sir Benjamin Collins Brodie professor of Chemistry at Oxford, from 1855to 1873. He was hörn in 1817 in London and died in 1880.

2 Notice on further experiments as to the reduetion of metallic Oxides bythe peroxide of barium. Chem. Soc. Journ. vol. 7. 1855. p. 304.

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