Faraday to Charles William Pasley   9 March 1837

R Institution | 9 Mar 1837

My dear Sir

I have been engaged the last three or four day[s] in analyzing your clays¹. (You know analyses are very tedious & time consuming things) and now send you the results[.]

The pit clay in its moist state has a specific gravity of 2.07. This you required to know though I do not see what use it can be of to you. It contains a trace of carbonate of lime but it also contains little calcareous concretions like small pebbles which would render a specimen carelessly taken very uncertain in its composition[.] In its moist state as sent to me a hundred parts contain the follow‑ing proportions very nearly

The Medway clay in its dark coloured & moist state had a Specific Gravity of 1.46 but this of course would vary as the quantity of water varied. 100 parts gave

I have put down all the iron as per oxide because it is the best state in which to estimate it but in the clay whilst dark coloured a portion of it is in the con‑dition of Sulphuret (the greater portion being even then per oxide) and the presence of this sulphuret causes the dark colour & also the evolution of Sulphuretted hydrogen upon the affusion of acids - a little protoxide may also be present[.]

The gases you speak of as existing in the clay do not exist in it really but are produced from the wood & organic matter - the carbonate of lime & the Sulphuret of iron &c &c by the action of heat[.]

Ever Dear Sir | Very Truly Yours | M. Faraday

Coll. Pasley | &c &c &c

Address: Coll. Pasley | &c &c &c | Chatham