Faraday to Marc Isambard Brunel   9 February 1836

Royal Institution | 9 Feby 1836

My dear Sir

I think my best plan will be to answer your four questions first¹ and then add an observation or two; but I understand that the coal gas I have to think about is always that made from cannel coal and therefore like that of Edinburgh. Then as to

Query 1st. I do not think that the liability to explosion is greater with such coal gas than with oil gas; nor do I think that (with very moderate precautions) you need have the least fear of explosion from either of them in such a well ventilated & well regulated place as the Thames Tunnel[.]

Query 2nd. I have not lately had occasion to compare coal and oil gases but I have formerly seen coal gas from Parrot coal which appeared to me to be as pure as oil gas: & I think you need not expect any serious objection on that score[.]

3rd. The heat evolved by the best coal gas is not so great as to excite the apprehension you speak of in the Thames Tunnel especially if you can apply a principle which I will almost immediately suggest to you[.]

4th The quantity of moisture from such coal gas as we speak of does not I think (judging from former experiments) form an objection to its use in the Thames Tunnel[.]

But why not clear away all these doubts at once by receiving the products of the combustion of the gas whether oil or coal gas into bell shaped vessels or other apertures connected with a ventilating system so as to carry them out of the Tunnel at once & prevent them from mixing with the air in it[.] In this way all possible bad effect from the heat, moisture &c will be done away with and I should think rather benefit than disadvantage be produced. The expence would be but small & the effect I think complete[.]

I am My Dear Sir | Most Truly Yours | M. Faraday

Mark I. Brunel Esq | &c &c &c