To Edward Cresy   29 April [1853]¹

My dear Sir,

I am uncommonly much obliged to you for your note which has been of the greatest use to me. From what you say, I will try the siphon plan, with 1$\frac{1}{2}$ inch pipe, which was just what I wanted to know. What you say about a good pump being required to fill the siphon, has made me think of my hydropathic Douche Pump (not now used)² which is a three inch lift pump and stands just in the right place. I will try a union joint (as you suggest) but at only one end, and will, when filled, plug it up, lower it in the tank to be filled, and then by a string and stick pull out the plug.

I am also very grateful for suggestion about the 9 inch ribs of Brickwork which shall be done. In your section, I see that the extra and upper half-brick work does not bond with the lower half-brick, and I suppose this is intentional, for Mr. Lastell³ told me before, that in strengthening a dome all over, the upper course was only cemented on the lower, not bonded into it. If I understand your section wrong, perhaps you will send me a line: if I do not hear, I shall understand that I am right.

The only point on which I am doubtful is the kind of hose: it will be seldom used, and I will call on Burgess & Key⁴ and see what they say about their canvas hose coated & lined for the douche, and used for watering gardens with pure water or liquid manure. This is only 9d per foot, 1$\frac{1}{2}$ inch bore. I shd. grudge much more expense for my plan.

I hope sometime in the course of the summer (part of which however we shall be away)⁵ to persuade you to pay me a visit for a day or two.

With very many thanks for your valuable advice, | Sincerely yours, | C. Darwin.

At the same time I wrote to you I sent the same question to the Gardeners’ Chronicle⁶ but it now turns out through your kindness quite superfluously.