PROGRESS OF ASTRONOMICAL PHOTOGRAPHY. 197 



ages to reach the final finish and last perfection in the calculation of 

 the tables of the motions of the moon and the planets, to eliminate 

 any element of error, however minute, and to detect any latent dis- 

 turbing force, however feeble its effect; yet it is to private observato- 

 ries and to observations made in the remoter regions of starry space 

 that we are chiefly to look for new discoveries. It augurs well for 

 the future that there is no lack in our own day of such establishments, 

 or of accomplished observers to use them. It is almost, if not alto- 

 gether, needless to bring before you the names of Admiral Smyth, or 

 Lord Rosse, or Mr. Lassell, or Lord Wrottesley, or Mr. Dawes, or 

 Mr. Carrington, and a host of others familiar to many of you. The 

 elliptic motions of binary stars round their common centre of gravity, 

 the colors of others, the discovery of new planets, the calculation of 

 cometary orbits, the laws of change in the variable stars, the sudden 

 burst upon the sight of some stars, and the gradual evanescence of 

 others, will afford for many generations suitable and exhaustless sub- 

 jects of sustained astronomical research. The instant splendor and 

 gradual decay of certain stars is one of the most wonderful facts re- 

 corded in the history of astronomy. In 1572, Cornelius Gemma ob- 

 served a star in the chair of Cassiopeia^ transcending Venus herself 

 in brightness. It was Hipparchus who first, I believe, noticed the 

 sudden appearance of a star of singular brilliancy before unknown. 

 By this strange discovery he was urged to construct a catalogue of 

 stars visible to the naked eye, "that posterity might know whether 

 time had altered the face of the heavens." 



■ The art of photography is of the very highest importance in the 

 promotion of exact science. 



It stereotypes, so to speak, for the use of all time to come, the 

 present aspect of the heavens. 



As astronomical observations ranged in tables record the present 

 positions of the heavenly bodies, so photography registers their pres- 

 ent aspect. It may be that the pictures of the sun now taken will 

 enable future ages to test the prediction of the poet, 



" The stars shall fade away, the sun himself 

 Grow dim with age, and nature sink in years." 



If, then, we take collective note of all Mr. De La Rue's long and 

 varied labors since the 14th March, 1851, when he became one of our 

 members — such as the perfecting of the figures of mirrors, the graphic 

 observations of the planets, tire incomparable photographs of the 

 moon, the invention of the photoheliograph, the observations on the 

 solar eclipse, the invention of the new method of obtaining numerical 

 data, the application of the stereoscope to the examination of the sur- 

 face of the moon, and afterwards to that of the sun — sure am I that 

 the society at large will unanimously approve of the award of their 

 medal made by the council. 



It may, however, be said by some ingenious critic that photography 

 is only an art which bears but indirectly on the promotion of astron- 

 omy, and that the reward of its suceessful manipulation is rather thte 

 province of those societies to confer which cultivate the art of pho- 



