WCP2884

[1]^{1, 2}

10 AMPTON ROAD

EDGBASTON

BIRMINGHAM

21 Sep[tember] 1907

Dear Sir,

I think your argument in the Chapter which you have sent me perfectly sound in general and I do not see how Prof[essor] Lowell can get over it. But of course he will for he starts from a hypothesis much more certain to him than any mere facts.

There are two of three details on which I continue to suggest altervatives

p66 Omit "if not absolutely to reach."

p70 The one per cent of radiation does not imply 1/100 of the temp °.

[2] but ⁴√1/100 = 1/3.2 about or about 160°absolute

p77 the effect of corrugation[?] of the moon's surface is I think that the rise in temperature is less during heating as you point out but during cooling the total radiation out from the planet will be the same as if the surface were smooth.

For if we have a section thus

ACE

/ \ / \ / \

XBDY

AB will radiate to BC & BC to AB & so on. The amount escaping out will be the same [3]³ as from a flat surface XY.

In my own paper I have purposely used Lowell's own data & those only to show that his results are untrustworthy. But his data I am quite convinced are quite wrong somewhere.

Thus he takes the Martian atmosphere as having the same effect our atmosphere above Camp Whitney. His data therefore make the temperature which should prevail at Camp Whitney higher than that at sea level. But we know that at such high level as Camp Whitney it should be much actually is much less. His data then are wrong.

I have made some calculations trying to take into account the alterations of day & night to the steadying effect of the air. But trustworthy data are wanting [4]⁴ & I do not see how to account with the data Lowell gives for this certain fact that the less the atmosphere [1 word illeg.] terrestrial surfaces the colder those surfaces are.

It is remarkable that the atmosphere above the surface can hardly cool at all during the night except near the ground. This comes out at once if we consider what great mass it has & what poor radiating power it possesses.

I will send you my Phil [1 word illeg.] proof when I get it. But you appear to me to have all the general ideas set forth without quoting it if it does not come in time.

I shall be very glad to read the proof of your next Chapter if you will kindly send it me.

Yours faithfully | JH Poynting [signature]