470   .Li, f e and Letters of Francis Galton

We heard two days ago from Mrs i2cLennan's *sister, who says that she (Mrs McL.) has been nearly dying but that she is now somewhat better. They are preparing for leaving Davos, and are inquiring for a good place-to go to. I am sorry to hear that your visit of charity did little good to your own self. It was very good of you to go. Ever yours, FRANCIS GALTON.

August 12, 1880. Excuse badd paper, ink, etc.,- our house is in the plasterers' hands.

DEAR GEoRGE, The enclosed was sent to me asking me to read it and forward it to you. , The writer, Walter Smith; was a' bracketted 2nd Wrangler some few years back and of Trinity College-you would know all about him. I knew his people well, especially his father, Archy Smith.

Did I tell you that during a happy day I spent among the idiots at Earlswood I learnt from the very intelligent medical director, Dr Grahame, that his inquiries about the parents of the idiots quite confirmed your conclusion about cousin-marriages, and that he bad said so in print?

I suggested to W. Smith that if he wished to work up the subject de novo he should get an old Burke's "Peerage" and "County Families" and pick out the first hundred or so cousin-marriages, also of ordinary marriages that he came across, and partly by the help of more recent editions but chiefly by that of gossips about the aristocracy compare the results. If the difference was not a notable one he might be at rest as to harm done by not forbidding the banns. I wonder if -he has a personal interest in the inquiry. What a charming episode in a novel-the' conscientious young Scientist collecting laborious statistics before he ventured to propose.

We go to McLennan's to-day, to stay till Saturday afternoon at Hayes Common.

Ever yours, FRANCIS G'ALTON.

P.S. Thanks for grouse.

42, RUTLAND GATE, S. W. December 11, 1881.

MY DEAR GEORGE, Here are the three sets I circulated of Mental Imagery questions.. They were usually followed up by correspondence.

What a wonderful application of your earth-history theory is this big. tide in early. geological times ! I want particularly to read your account of the matter when it appears, and to have your own views thereupon. It is a grand idea indeed-the grandest since the Originn of Species. Have you thought over the corresponding air tidal-wave? Now, in the tropics, the diurnal barometric range is (... I say inch), what will it have been in those times? And what. would be the corresponding wind force? I. can't understand how, any thing could live on dry land, under such blasts. Talk of catastrophes, why, that time must have, been a continual series of catastrophes. Dante's Hell is nothing to it. But I had rather have the facts from. you than through the Astronomer Royal of Ireland. Don't of course bother to answer this, but I hope we shall soon read a short article from you in Nature or somewhere on this , extraordinary revolution in old ideas.

Have you too (I ask not for an answer) talked overor thought about the air flying off from the earth, and notably from the moon, to somewhere else? I mean what we were talking about. Lord Rayleigh seemed to think it worth considering and within range of calculation. Just now I suppose you are busy up to the eyes with Tripos preparations. We look every morning in the column of births in the Times for news from brace t. Ever yours, FRANCIS GALTON.

THE ATHENAEUM. December 11, 1881.

What frightful nonsense I have just despatched in a' letter to you about air-tides. There was conversation-I had two ideas in my head and they blundered "together as in a dream, the letter went and I could not correct it.

In sober sense I should have written: Supposing height of air-tide in an, imaginary homogeneous atmosphere to be the same height as water-tide (Herschel says so), say 8 feet, then the corresponding barom. pressure due to air-tide would be 0.008 inch. Under the supposed ancient condition of a 216-fold height of tide this would become 216 x 0.008 =1.728 inches, so that the barometer would go up and down 1 i inches in every 12 hours, which implies a constant state of hurricane. F. 0.

* The wife of Donald McLennan, the writer of The Patriarchal Theory. fi Horace Darwin, Charles Darwin's fifth son.