Dear Darwin

About Worms:— I have waited for an opportunity of verifying what I told you about the effect of heavy soaking rain, when it suddenly succeeds moderate weather, in driving the worms from their holes to the gravel walks, where they crawl for long distances in tortuous courses, & where they die.¹ It has been very frequently observed by me in Hyde Park & this morning, I have again witnessed it in a sufficently well marked degree to be worth recording.

It rained heavily on Saturday night last, after a spell of moderate weather. Unluckily I was not in the Park on Sunday till near 1^h., by which hour the birds had had abundant time to pick up the worms. Still, dead worms were about & their tracks were most numerous. On Sunday (last night) it again rained heavily & I was in the Park at 10^h. The tracks were not nearly so numerous as they had been on Sunday morning, but more dead worms were about. I began counting, & found they averaged 1 to every 2$\frac{1}{2}$ paces (in length) of the walk, the walk being 4 paces a trifle more in width.

Walking on, I came to a place where the grass was swamped with rain water on either side of the raised gravel path, for a distance of 16 paces. In those 16 pace-lengths I counted 45 dead worms.²

On not a few previous occasions when I have been out before breakfast, I have under the conditions already mentioned seen the whole of the walks strewn with worms almost as thickly as were the 16 pace-lengths first described. The worms are usually very large. I rarely notice dead worms on the paths at other times

Ever sincerely y^rs | Francis Galton

I shall be very curious to learn about the effects of the red light as against those of a strongly actinic colour³