Thomas Beddoes to Erasmus Darwin, [?November 1787]
Dear Sir,
I just receive your letters when I am going through a course of lectures with, I believe, the largest class that ever was assembled in Oxford, at least since the discovery of Justinian’s code drew together thirty thousand students. And I think some of your specimens would suit the purpose I have in view in giving them, for I touch upon many points of physical geography. To any one who is at all interested in subjects of that nature, an invitation such as you send must be extremely welcome. I hope nothing will prevent me from reaping the benefit of it.
To your difficulties about coal I should be able to return a ready answer, if reflecting upon the very same points could have furnished me with it. The facts which have catched my attention as applicable to your first question are, that subterraneous strata (I use this term in contradistinction to superficial peat) of peat have been found intermixed with clay. Now I conceive that that peat must have been removed by water and deposited, as other strata; at the same time that a quantity of clay was brought from some different quarter. If so, was peat converted into coal by the action of fire in its present situation? the state and particularly the softness and looseness of the strata that alternate with coal, seems a formidable objection to this supposition. Was peat or were vegetables in general converted into coal and then washed away and deposited? I have specimens of brecciated coal; I have pebbles of coal in very ancient strata, as in hard sandstone; so that coal must have existed before the accumulation and consolidation of those strata; and if it was rolled into pebbles, it might by the same means have been reduced to smaller particles and so deposited from water.
Give me leave to say that your third question is not quite precise. The term goodness may mean power of giving heat or freedom from sulphur, and perhaps it may express some other relation. You, I dare say, mean its comparative power of heating; and I think it certain that as more bitumen has been driven from it, it will give, cæteris paribus, more heat; because the act of throwing off bitumen, as in common grates, must absorb heat: and the same quantity of coal we well know will give about one-third more heat in the form of coak.
By combining another fact with Cavallo’s observation, we may get at some comprehension of it. Water in boiling, chalk and vitriolic acid, and I suppose iron too, produce strong signs of electricity, and that may affect the needle, if it be really affected, as Cavallo says.
There are at least two ways in which a man may expose himself, by asking questions or by giving responses; the latter seems to me at present much the more dangerous; and therefore you, in your prudence, have chosen the better part and left me the risk. As a compensation, I beg to change sides and to ask, whether you or any of your friends see any light streaming from the facts to which I have alluded upon the difficulties proposed; and if so, whether they can add a few more, in order to dissipate the darkness entirely? I beg the favor of you to send the fossils hither and as soon as may be; and am,
Your’s very respectfully,
Thomas Beddoes.
Published: Stock, Appendix 6, p. xxxvi–xxxvii