342 



SCIENCE. 



[N. S. Vol. VIII. No. 194. 



"It is not improbaWe, likewise, tliat this art (still 

 in its infancy) when it approximates to perfection, 

 may enable us to take representations of the sublime 

 objects of the heavens. The sun affords sufficient 

 light for this purpose ; and there appears no insur- 

 mountable obstacle in taking, in this way, a highly 

 magnified picture of that luminary which shall be 

 capable of being again magnified by a powerful 

 microscope. It is by no means improbable, from ex- 

 periments that have hitherto been made, that one 

 may obtain an accurate delineation of the lunar 

 world from the moon herself. The plated discs pre- 

 pared by Daguerre receive impressions from the action 

 of the lunar rays to such an extent as permits the 

 hope that photographic charts of the moon may soon 

 be obtained ; and, if so, they will excel in accuracy 

 all the delineations of this orb that have hitherto 

 been obtained; and, if they should bear a microscopic 

 power, objects may be perceived on the lunar surface 

 which have hitherto been invisible. Nor is it impos- 

 sible that the planets Venus, Mars, Jupiter and 

 Saturn may be delineated in this way, and objects 

 discovered which cannot be descried by means of the 

 telescope. It might, perhaps, be considered as be- 

 yond the bounds of probability to expect that very 

 distant nebula; might thus be fixed, and a delinea- 

 tion of these objects produced which shall be capable 

 of being magnified by microscopes ; but we ought to 

 consider that the art is yet in its infancy, that plates 

 of a more delicate nature than those hitherto used 

 may yet be prepared and other properties of light 

 may yet be discovered which shall facilitate such 

 designs." 



Had Dr. Dick lived until the present day- 

 he would be amazed to see what portions of 

 his prediction have in a measure come true. 

 To him the most improbable of the things 

 he forecast for photography to accomplish 

 was the delineation of the nebute, and yet 

 it is in this direction that photographic 

 astronomy has most decidedly excelled. To 

 use highly magnified images for photo- 

 graphing the details of the planets seemed 

 to him to be among the first triumphs that 

 were to fall to astronomical photography ; 

 yet to-day they are almost as far from 

 realization as they were in the days when 

 good Dr. Dick charmed his readers with 

 vivid descriptions of the wonders of 

 astronomy. I do not think the most 

 active imagination could have foreseen in 



Dr. Dick's day the marvellous extent to 

 which astronomy at the close of the nine- 

 teenth century would be influenced by that 

 light-picturing process just then being de- 

 veloped by Daguerre and others. 



After all, however, it is easy in the case 

 of great discoveries of this kind to predict 

 what they will amount to. This is usually 

 done by immensely exaggerating all their 

 possibilities and thus, by a happy chance, 

 hitting one or more of their realities, for 

 strict account is usually kept only of the hits 

 in such cases, the misses being rejected by a 

 charitable world as a matter of no impor- 

 tance. We are used to wonders in the se days 

 of wonders, and have a happy habit — from 

 frequent practice — of correctly guessing the 

 outcome of some of the great discoveries. 

 But when Dr. Dick wrote, these things were 

 not so easily foreseen, for the possibilities 

 of the sciences were not so apparent then as 

 they are now. 



So great have become the possibilities of 

 photography in the astronomical investi- 

 gations of to-day that an account in detail 

 of its accomplishments would far exceed 

 the limits of this paper, and for that reason 

 I shall be forced to a brevity in dealing 

 with this subject that must necessarily pass 

 over many of the interesting things pho- 

 tography has done for astronomy in its 

 comparatively short lifetime. 



It does not come within the province of 

 a paper of this kind to deal with the ques- 

 tion of priority in the discovery of photo- 

 graphy (though something might be said 

 on that point for America), as the process 

 interests us only in so far as its application 

 to astronomy is concerned. 



It appears that on the very first announce- 

 ment of Daguerre's wonderful discovery on 

 the 19th of August, 1839, the celebrated 

 French astronomer Arago, who addressed 

 the Paris Academy on the subject, quickly 

 foresaw the great advantage it must neces- 

 sarily be to the science of astronomy, espe- 



