34° 



POPULAR SCIENCE MONTHLY. 



plete rotations, and the side originally viewed will be visible 

 again. 



Owing to the rotundity of the planet, only the central part of 

 the disk is sharply defined, and markings which can be easily seen 

 when centrally located become indistinct or disappear altogether 



Eclipses anu Tkansits of Jupitek's Satellites. Satellite I and the shadow of III arc 

 seen in transit. IV is about to be eclipsed. 



when near the limb. Approach to the edge of the disk also causes 

 a foreshortening which sometimes entirely alters the aspect of a 

 marking. It is advisable, therefore, to confine the attention main- 

 ly to the middle of the disk. As time passes, clearly defined mark- 

 ings on or between the cloudy belts will be seen to approach the 



