Warren De La Rue to Faraday   25 April 1861

The Observatory, | Cranford, Middlesex. | W. | April 25 1861

My dear Faraday

The following particulars of the Eclipse you may like to have¹

The Sun’s semidiameter 15’ - 44”.8

The Moon’s computed for my station at the epoch of totality} 16’. 33”

The ratio of the Moon’s diameter to the sun’s diameter measured on the photographs is as 1.05244 to 1 which gives you the Moon’s semidiameter }16’.34”.3

Duration of totality at my station } 3min - 25 sec

Motion of the Moon during the totality computed } 93”

Measured on photographs 93”.4

Motion during one minute the time of exposure of the first plate} 27”.22

Measured on No 1 Photograph 23”

The nearest approach of the centres of the Sun & Moon } 14”

<->

Arrived at Bilbao 9th July partially overcast

10 -- do do

Arrived at Risabellosa 11 -- cloudy

Instruments arrived in the evening

Got the meridian by Sun’s observation 12 partial cloud

13 half cloud

first solar photograph 14 cloud in morning clear afternoon

15 cloudless

16 cloudy

17 cloudy

day of eclipse <-> 18 cloudy up to 11h. 38 min

A photograph lost by clouds passing over the Sun } at 2h. 12min

In respect of the amount of light at the period of totality:- I am inclined on reflecting to think that the light in the sky must after all have been greater than that of the sky illuminated by the full moon because assuredly fewer stars were seen at the period of totality than are visible at the epoch of full moon. The colour of the light was unquestionably very different from moon light and the appearance of objects illuminated by it so very different to that we ever see under ordinary circumstances that it is difficult to render an exact account of it even to oneself and almost if not quite impossible to impart to others any idea of the peculiarity of the phenomena we witnessed. Grand beyond description was the appearance to the naked eye of the dark bronze moon surrounded by the silvery corona in a sky of an intensely dark indigo blue in its immediate neighborhood but passing through a sepia tint into a very bright orange close to the horizon. The distant mountains appearing, perhaps by contrast, of an intense blue. The colours of all objects completely changed, they were all dulled and to my eye a sort of violet-bronze tinged all things at a little distance yet the paper on which I was drawing still looked white & I could distinguish very well the various tints I had prepared to compare with the luminous prominences. It required a very strong mental effort to recall me back to my real task when I had once lifted my eyes away from the telescope, & I heartily regretted at that time that I had ever undertaken to head the photographic expedition.

Yours Very sincerely | Warren De la Rue