My dear Father,

I have been to see Maxwell today & got his answer to y^r. question, which agrees with what I conjectured.¹

A thin film of air entangled in a rough surface which water does not wet, will prevent the body under it from drying so rapidly as it w^d. otherwise do. Through that film the vapour can only pass by diffusion, whereas if the moist surface were bare, convection would come into play; more or less fresh dry air would be brought near the surface & into this the vapour w^d. pass much more rapidly. He illustrated it thus   A field covered with dry stalks of corn will keep the ground moist much longer than without the stalks because the air entangled in the stalks gets moister than the rest of the air & will keep the dryer air from access to the moist surface of the ground.

If however you were to replace the stalks by lamp wicks which suck up the water by capillary attraction then there is a continual subtraction of water from the ground which w^d. evaporate easily from the tops.

There is not however more evaporation from a corrugated moist surface than from a flat equally moist one.

Thus a hygroscopic bloom on fruit would not keep the fruit dry, nor yet would it evaporate more rapidly than a smooth surface. I think this meets your views exactly.

My own work goes on excellently & I think I shall make a really good hit with it; I have got to do some fearfully hard work yet & I can hardly think of anything else.²

The proposal for y^r. LLD comes on at the next meeting of the Council of the Senate & I believe will be voted on on Thursday, but I don’t suppose there will be any opposition.³ I sh^d. think they w^d. propose some day towards the end of Nov & it will be a Thursday anyhow.

When does Jim come—⁴ Tell him Dew has got a telephone.⁵

Your affectionate son | G H Darwin