WCP1673

[1]¹

10. AMPTON ROAD,

EDGBASTON,

BIRMINGHAM.

19 October 1907

Dear Sir,

I have been very glad to have the opportunity of reading the last chapters of your book on Mars. I have found them very interesting.

I have no suggestions or criticisms to offer except on the point of increased radiation with thinner atmosphere.

Your explanation of a possible mode of formation of the Canals appears to be very promising. I like it.

I am sending you a paper² [2] ³ by Newcomb on the interpretation of the Canals which, if you have not seen it, may interest you. Please return it at your leisure.

As to the statement that the decrease of temperature with altitude is due to increase of radiation — I think this hardly gives the right idea.

The radiation from the surface decreases as the temperature decreases, whatever the nature of the air above. but [sic] the temperature from sun-heat increases first!⁴

I should rather put it thus: — The thinner air does not retain so much heat either of what it receives from [3] the sun or of what it receives from the surface & so does not send so much down to the surface.

In a denser atmosphere the radiation sent out does not escape so readily. More of it is absorbed & sent back. and [sic] at the same time more of the suns [sic] radiation is absorbed & sent back. ^{and some of this} is sent down [.]

Would it not be better to say that the decrease of temperature with altitude is to increase of escape of radiation?

I sent my paper to the Plul Maj some time ago [.] A week ago I asked for it back to correct an error in one of the formulae, which I have detected. But [4] I have had no acknowledgement of receipt nor answer to my request from which I gather that the editing is somewhat intermittent [.]

I enclose a few words which will perhaps serve your purpose [.]

Yours faithfully | JH Poynting [signature]

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