8 Life and Letters of Francis Galton
corona as a mock -halo. His job at the eclipse was to have been the taking of observations with an actinometerz, but on the day before the eclipse, when the instrument was unpacked, it was found to be broken.
"I candidly confess that a rising feeling of exultation accompanied this discovery; I was not now necessarily obliged to spend the precious three minutes of the eclipse in poring on an ascending column of blue fluid in a graduated stem, and noting down the results by feeble lamplight, but I was free to enjoy to the full the whole glory of the eclipse." (V.T. 1860, p. 437.)
Galton decided to sketch the corona and to determine from its effect on colours the exact colour of the eclipse light about which there had been controversy. His account2 of the eclipse is worth reproduction in part, if only for the originality of his views on the corona.
"2 hrs. 50 m. Indian yellow, cobalt and emerald green are lower in tone. I can distinguish all twelve colours perfectly. Light much fainter. 55 m. Light far fainter. I made a hole in a paper screen, and watched the crescentic image of the speck of sunlight that shone through it on the floor. The shadows were very dark and sharp. Air cold. 58 m. The numerous pigeons of the place began to fly home, fluttering about hurriedly, taking shelter wherever they could. There was something of a hush in the crowd.
At about 3 h.-I forgot to note the exact watch time, I am sorry to say-totality came on in great beauty. The Corona very rapidly formed itself into all its perfectness. It did not appear to me to grow, but to stand out ready formed, as the brilliant edge of the sun became masked. I do not know to what I can justly compare it, on account of the peculiar whiteness of its ' light, and of the definition of its shape as combined with a remarkable tenderness of outline. There was firmness but no hardness. In its general form, it was well balanced, but larger on one side than the other. It reminded me of some brilliant decoration or order, made of diamonds and exquisitely designed. There was nothing to impress terror in the sight of the blotted-out sun; on the contrary the general effect of the spectacle on my mind was one of unmixed wonder and delight The Corona-light sufficed abundantly for writing rough notes and for seeing my colours. Oddly enough, the burnt sienna and the vermillion alone ceased to be distinguishable from each other. Indian yellow had greatly lost brilliancy. I made a rough sketch of the Corona-it was too manifold in its details and too beautiful in its proportions for me, bad artist as I am, to do justice to it in the short time the spectacle lasted-yet the drawing which I made and which is given here [see Fig. 1, p. 9], is to my mind a fair diagram of this splendid meteor'. I drew it without taking any measurements to guide me, but simply as I would sketch any ordinary object. The uppermost part is that which was uppermost when I drew it. I used no lantern and required none; there was a sufficiency of light. The principal facts were, firstly, that the long arms of the Corona [see Fig. 2, p. 9] do not radiate strictly from the centre, neither are they always bounded by straight lines'. The upper edge of a was truly tangential, that of d and others nearly so; c was remarkably curved, and so was the lower edge of b, though less abruptly; it was like a finch's beak, and remarkably defined. Secondly the shape of the Corona was not absolutely constant; speaking generally, it was so; but in small details it appeared to vary continually, by a slow diorama-like change. There was no pulsation or variation of intensity, visible in its light. I was particularly impressed by its solemn steadiness.
' Galton had previously to his departure been instructed by Sir John Herschel in the use of this invention of his.
2 His sketches and other details appear in the Royal Astronomical Society's Memoirs, Vol. XLI, pp. 563-4, as well as in Vacation Tourists.
3 Elsewhere in this paper (p. 423 "each phenomenon of that strange and magnificent meteor ") Galton uses this word in the sense of an unusual atmospheric appearance.
4 Even Sir George Airy doubted the curvature Galton gave to some of his rays, but photographs of subsequent eclipses have confirmed the curved rays. There was no photograph of this eclipse, the first probably at -which photography was possible, although a photographer was present. He inserted his slide and exposed, but had forgotten to put a plate into his slide!