468 Life and Letters of Francis Galton
give a stereoscopic image of the lower clouds must be disposed right and left to give one of the upper clouds.
I fearthat our-real difficulty will relate to time of exposure. I should propose to begin by taking four or five consecutive pictures at somewhat different degrees of exposure, and seeing what can be learnt from them in every way, including various stereoscopic combinations-and will certainly follow your suggestion of making the first trial on a suitable cloudy day, as well as the other suggestion in your letter. Sincerely yours, FRANCIS GALTON.
42, RUTLAND GATE, S. W. October 23, 1879.
My DEAR PROFESSOR*, About MacAlister's paper; it might be well to look at the marked passages in the enclosed letters from him, sent to me a few days back. Do not return them.
The principal people who have used the law of error for vital statistics, since Quetelet, are the compilers of the War Department Statistics of the N. American Forces after the war between the N. and S. States. And again, curiously enough, Fechner himself in his Psychophysik (i, 108) introduces a long mathematical investigation by his mathematical colleague (I have lent the book and forget his name) wherein a series of law of error tables, "Methoden der richtigen and falschen Falle," are formed to help him in his own investigations. In short, he ignores his own law! He uses tables on the Arithmetic Mean principle to discuss results of observations on phenomena that have the Geometric Mean condition. So the question treated in the paper is really one of importance to statisticians.
Very sincerely yours, FRANCIS GALTON.
42, RUTLAND GATE, S.W. October 14, 1879.
DEAR SPOTTISWOODEt, I venture to enclose some suggestions for increasing the interestnegatively if not positively-of the meetings of the Royal Society. If they seem reasonable to you, perhaps the Council would in due time take them into consideration. The recognition of the fact that very dull papers do not need to be read at all,. and that difficult papers should not be discussed after only one simple reading of them, would I think be a boon. I fancy, too, that under the proposed plan the experimental part would gradually develop and. the discussions ought certainly to improve. I have talked the matter over with a few persons and thus far with a favourable result, but I leave the matter to your much better judgment.
Ever sincerely yours, FRANCIS GALTON.
Suggested procedure for the Meetings of the Royal Society.
The first publication of a memoir by the Royal Society to be not as at present by reading it to the meeting, but by laying revised copies of it, printed in sheet with paper cover, title and date-in fact, the author's copies-on the table and reading the title only.
The subsequent issue of the memoir in the ordinary publications' of the Society to take place exactly as it does at present.
The subjects advertised for such meeting should generally be memoirs that had previously been published. The authors or their deputies should give explanations of them, illustrated as far as may be by experiments and drawings, and followed by discussions. The President to have full power as at present to. select the subjects for the meeting and the order of taking them. For the most part they would come before the Society in one or two weeks after their publication. Some however would never be brought forward at all, and others would perhaps be most advantageously discussed on the same day as their publication.
42, RUTLAND GATE, S.W. October 23, 1879.
MY' DEAR MISS HERTZt, Please accept by letter, as you were out when we called and I could not verbally give, our very warmest congratulations and best wishess for many years of future happiness. I can assure you that I think your intended ought to consider himself
* Professor G. G. Stokes. The letter refers to Donald MacAlister's paper on the Law of the Geometric Mean see our. Vol. ii, pp. 227-8.
t President of the Roal Society 1878 to 1883.
I Daughter of Mrs Hertz (see p. 464 above).