WCP188

[1]

Broadstone, Wimborne

Sept^r. 20th. 1907

My dear Will¹

The cutting you sent about Lowell² & Mars³ is well written & shows more knowledge than most newspaper articles in Science. I enclose you a bit about "Kipling"⁴ which is interesting.

I am glad to say Prof. Poynting⁵ of Birmingham is going to reply to Lowell’s math^l paper. I have already done what you suggest — keeping to general arguments, & not giving figures, except where they are generally accepted. [2] I have now finished my article ^or book^,6 and think it will be both strong and generally interesting. It makes 8 chapters and perhaps about 120 — or 150 pp.

I have sent the Chap. on my "Estimate of the Temperature of Mars" to Prof. Poynting, & when I get it back shall send the MSS. to Macmillan[.]

The main point I should like to have settled mathematically is, about the moons temperature being possibly affected by its [3] long day & night. The question would be "Will the mean temperature of a planet (or satellite) be altered if the rate of its rotation (length of its day) becomes lengthened — say to doubled?"

Mr Osmond Fisher⁷ thinks it will be increased. I am pretty sure that — if altered — it will be diminished.

It is of course a problem if the balance between radiation and absorbtion [sic], which is determined by Stefan’s Law, that — the rate of radiation increases as the [4] 4th. power of the absolute temperature.

I think this ought not to be difficult to work out. Ask your friend if he can do it — if only to decide whether the temp. will rise, fall, or remain unchanged.

It will simplify it to take the case of a body without air like the Moon.

Your affectionate Pa | Alfred R. Wallace [signature]