298 IN STARRY REALMS. 



considerable share in our further study of this the 

 most gigantic of our planets. The marks on Jupiter 

 are so incessantly varying that the photograph seems 

 obviously the true method for recording its ever-fleeting 

 details. It will be noticed that the circumstances 

 are here quite different from those which attend the ap- 

 plication of photography to the moon. In the latter the 

 features are permanent, and the efforts of the eye and of 

 artistic sketching can be persistently accumulated, with 

 the result of giving us a delineation of the lunar surface 

 as faithful as the powers of our telescope will permit. 

 But there is no permanency in Jupiter, and our only 

 means of becoming acquainted with the marvellous mete- 

 orology of that planet must be derived from the bringing 

 together of as many accurate pictures of its disc as can 

 be obtained in its ever-varying moods. For this object 

 photography seems most admirably adapted. There is, 

 however, a point which should be mentioned, and it has 

 been brought before us very strongly while examining 

 the beautiful Jovian photographs taken by the Henrys. It 

 is that the photographic Jupiter and the visual Jupiter 

 are different pictures. This is no doubt largely due to the 

 atmosphere of the planet, which exercises a different 

 degree of absorption on the photograph rays from that 

 to which the visual rays are exposed. Here again the 

 difference between the problem of photographing the air- 

 less moon and photographing a planet becomes significant. 

 In the case of the moon the visual picture and the 

 photographic picture tend to coincidence in proportion as 

 they both approach perfection. 



Pleasing pictures have also been taken of Saturn, es- 



