Faraday to James Richard Clark   29 May 1835

Royal Institution, 29 May 1835.

Sir,

I have hastened to answer your letter as soon as I possibly could make the experiments, but am much pressed for time at this period of the year¹.

In the cube of elm, the corrosive sublimate may be traced inwards to a depth from one-fifth to one-fourth of an inch, by the ordinary tests: by the test of voltaic action, I could trace it at the depth of three-fourths of an inch, and I think there were appearances at the depth of an inch, but they were doubtful; beyond that there were no indications.

In the cube of oak, the corrosive sublimate was easily found at the depth of one-fifth or one-fourth of an inch by the usual tests, but it was irregular, and apparently followed the fissures in the wood. By voltaic action I could not trace it quite so far into this wood as in the elm.

Cube of fir. The penetration here was in the smallest degree; the corrosive sublimate could be traced inwards about one-eighth or one-sixth of an inch, by hydr. sulphuret of ammonia, and about half an inch by the voltaic battery. The turpentine in the wood had probably been the obstruction to penetration.

From these results, I am inclined to think that what I found at the depth of four inches in Mr. [M.I.] Brunell's wood may have been carried in by the saw, as that piece was a sawn plank and not a cube. But I do not know the history of that piece, except as reported to me².

The bottles No. 1, and No. 2, contained the same proportion of corrosive sublimate in solution, and that was 176 grains to the imperial pint, as nearly as I could carry the experiment in the time I had to give to it³.

I am, &c. | (signed) M. Faraday

- Clarke, Esq.