WCP186

[1]

Broadstone, Wimborne

July 16^th. 1907

My dear Will

Am very glad to hear you have pleasant lodgings in such a healthy situation, though it seems a long way off. I see by the Map there are hills over 1400 feet high only 12 miles from Saltburn S. by W., and that is just ^about the same distance as we are from the Purbeck hills, which are less than half the height, yours ought to look almost mountainous.

As I did not receive any reply from D. Scott to my ultimatum by the 2nd post on Monday ^(yesterday) I at once wrote to Hardwicke & Blaber asking them to take immediate proceedings. I will let you [2] know how it goes on.

If any of your office-friends are well up in Physics ⁽Heat⁾ will you ask their opinion of the following argument as to the temperature (surface) of Mars.

1. It is generally admitted that our temperature depends wholly on Sun-heat, the interior heat (except perhaps locally) not affecting climate at all.

2. Mars, from its greater distance, receives less than half (.45) the sun-heat we receive. per unit surface?¹

3. Therefore — other things being equal — its resulting temp. should be [3] not more than half that of the earth. (Is this right?)²

4. The Earth’s mean surface temperature, is said to be about +8ºC. — The zero of Temp. is -274ºC. ∴ our absolute mean temp. is 282º above the absolute zero.

∴ Temp. of Mars 141º absolute = to -133C.

5. The difference of conditions are, that Mars has an atmosphere of at most a pressures of 4 miles of mercury, a cloudless sky, and ^very little — water-vapour. This would cause more insolation during the day, but much more rapid radiation during day & night.

[4] 6. Seasons & day & night almost exactly like ours — but year nearly twice as long.

Q[uer]y? Under these conditions what are the probable temperatures of Mars compared with ours?

Is it possible that (as Lowell³ assumes in his new book Mars & its Canals) its temperatures for a large part of the year is above O.C.1, instead of being, after all possible allowances, somewhere near 100C. below it O.C.2?

A reply with all possible speed will be acceptable. I have written, this two weeks, to Prof. Barrett⁴ of Dublin but having no reply fear he is away from home.

Your affectionate Pa | Alfred R. Wallace [signature]