196 PROGEESS OF ASTRONOMICAL PHOTOGRAPHY. 



eclipse in 1851, and of the solar eclipse in ISQO fotir small pictures 

 were also taken during the totality by Professor Monserrat, under 

 the direction of MM, Aguilar and Secchi, at Desierto de las Palmas, 

 in Spain. 



Mr. De La Rue, during tlie progress of the same eclipse, took many 

 large and exquisitely defined pictures, and secured two during the 

 totality. I have no need to enter into details, as he has already de- 

 scribed at several meetings of this society the numerical results that 

 follow from the discussion, and the comparisons of the photographs 

 which he took on that occasion. A paper giving the result of his 

 labors during the expedition to Rivabellosa has been presented to 

 the Royal Society, and is to be considered in March of this year. 



Mr. De La Rue has invented an ingenious micrometer, lately ex- 

 hibited at one of our meetings, by means of which he full}'^ confirms 

 the hypothesis that the colored protuberances belong to the sun, and 

 renders it almost certain that the commonly received diameters both 

 of the sun and moon require a correction. 



More recently still, photographic pictures of the sun have been 

 obtained by Mr. De La Rue, not only exhibiting its well-known 

 mottled appearance, but showing traces of Mr. Nasmyth's "willow 

 leaves," and by the aid of stereoscopic pictures rendering it certain 

 that the faculse are elevations in the sun's photosphere. 



I need not enlarge on the wonderful discoveries which have been 

 made and the astonishing results that have been obtained by Newton 

 and his successors in this the most fertile and exact of all the applied 

 mathematical sciences. Neither would it become me, an humble but 

 zealous worshipper of science, to hazard conjectures as to the/uture 

 progress of astronomy. And yet I cannot refrain from expressing my 

 belief that the success already achieved by our friend warrants us in 

 entertaining the hope that before long he will be able, with the aid 

 of stereoscopic pictures, to exhibit to us the rose-colored prominences 

 depicted on the sensitive plates as plainly as the faculse have already 

 been photographed. The depths and the successive strata of those 

 strange interlacing outliers within the solar spots may be brought 

 into tangible view. The different planes of Satitrn's rings* will also 

 come into relief, the belts of Jupiter may be manifested as portions 

 of his dark body, and ere long the mountains and elevated continents 

 of Mars will rise up into solidity before our delighted gaze. 



I may also, perhaps, be permitted *to remark, that while our gre>at 

 national and public observatories — indeed, I ought to say those of the 

 civilized world as well — are day by day adding to that enduring record 

 of the transient phenomena of the heavens Avhich.-will enable future 



* If the subject of the present address were not now of necessity confined to improve- 

 ments in celestial photography, I should here refer at some length to those exquisite and 

 unequalled hand-drawings by Mr. De La liue, of Saturn, JvpUer, Mars, and the comet of 

 1858, which have so often delighted and informed our society. They have embodied with 

 micrometrical accuracy the results of years of scrupulous and skilful labor ; and, as an in- 

 stance of the reliable nature of the results obtained, I may mention that, by placing under 

 the stereoscope two of Mr. De La line's hand-drawings of Saturn, taken at two distant 

 periods, the inclinations of the planes of the rings alluded to in the text become unmistak- 

 ably apparent. 



