My dear M^r Wright

I write today so that there shall be no delay this time in thanking you for your interesting & long letter received this morning.¹ I am sure that you will excuse brevity when I tell you that I am half killing myself in trying to get a book ready for the press.² I quite agree with what you say about advantages of various degrees of importance being co-selected, & aided by the effects of use &c. The subject seems to me well worth further developement.³ I do not think I have any where noticed the use of the eyebrows, but have long known that they protected the eyes from sweat. During the voyage of the Beagle⁴ one of the men ascended a lofty hill during a very hot day; he had small eyebrows & his eyes became fearfully inflamed from the sweat running into them

The Portuguese inhabitants were familiar with this evil as I well remember from a ridiculous incident; they immediately brought a woman who was suckling a baby to squirt milk from her breast into his eyes; but he “skedaddled” in dismay. I think you allude to the transverse furrows on the forhead as a protection against sweat; but remember that these incessantly appear on the forheads of Baboons.⁵

With many thanks believe me to be Yours sincerely | Charles Darwin

P.S. I have been greatly pleased by the notices in the Nation⁶