1866. | De la Rue and Celestial Photography. 365 
graphic accounts of these protuberances. They have also been 
noticed by other astronomers in all parts of the world. Sir John 
Herschel thus describes them: “ Distinct and very conspicuous 
rose-coloured protuberances were seen to project beyond the dark 
limb of the moon, likened by some to flames, by others to 
mountains, but which their enormous magnitude and their faint 
degree of illumination clearly prove to have been cloudy masses of 
the most excessive tenuity.”* 
In 1851, Dr. Busch succeeded in obtaining a Daguerreotype of 
the total eclipse of that year with the Konigsberg heliometer. In 
“i daguerreotype the protuberances were seen, but indifferently 
efined. 
In 1859, Mr. De la Rue commenced making the experiments 
necessary for securing a favourable photographic result, upon the 
occurrence of the total eclipse of 1860. The difficulties in the 
way of this were great. These will be gathered best from Mr. De 
la Rue’s own words: “I made inquiries of those astronomers 
who had witnessed the eclipse of 1851 respecting the intensity of 
the light of the corona and red flames as compared with that of the 
moon, and the relative brightness of one to the other, . . . . 
The general impression I formed from the information thus derived 
was, that the light emitted by the corona and red flames taken 
together was about equal to that of a full moon, less rather than 
greater; but no one recollected precisely the brightness of the 
prominences as compared with that of the corona.” Numerous 
experiments were made, and it was rendered evident that the 
utmost sensibility must be secured in the collodion plates to leave 
any hope of photographing those “cloudy masses of the most 
excessive tenuity.” The result of those preliminary experiments 
was that “nitrate of silver baths, prepared in the ordinary way 
with crystallized nitrate of silver, were taken and were used in 
depicting the several phases of the eclipse, with the exception of 
those of totality. In taking the latter pictures, the baths used were 
made with nitrate of silver which had been fused carefully in my 
own laboratory, and were so extremely sensitive that they would 
give photographs of the full moon in the focus of my reflector in 
less than a second of time, while with the usual bath five seconds 
were barely sufficient to give a picture of similar intensity.”} 
Thirty-four ewt. of apparatus, made up in thirty packing-cases, 
were conveyed to Spain in the ‘Himalaya,’ landed at the port of 
Bilboa, and thence conveyed to Rivabellosa, a distance of seventy 
miles, by the ordinary conveyances of the country. Everything 
was satisfactorily arranged, and “upwards of forty photographs 
were taken during the eclipse, and a little before and after it, two 
* «Outlines of Astronomy,’ edit. 1850, p. 235. 
+ ‘Philosophical Transactions, 1862,’ vol. clii., p. 334. ~ Ibid. 
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