OF THE COSMOS. NUMBER OF THE FIXED STARS. 99 



note all heavenly bodies which change their place, but whose 

 movements, from the faintness of their light, it would be 

 scarcely possible to perceive directly by the eye ; and in 

 this manner we may anticipate the discovery of all that 

 still remains unknown to us in our solar system. As 

 Harding' s excellent Atlas offers a complete picture of the 

 heavens, so far as Lalaude's Histoire Celeste, on which 

 it is founded, is capable of affording such a picture, so 

 Bessel, in 1824, after finishing the first section of his Zones, 

 formed the plan of founding thereupon a still more detailed 

 representation of the sidereal heavens, which should have for 

 its object, not merely the reproduction of observation, but 

 the systematic attainment of a degree of completeness which 

 should permit every new phenomenon to be immediately 

 recognised. The star maps of the Berlin Academy of 

 Sciences, sketched upon Bessel's plan, although they have 

 not yet completed the first proposed cycle, have already 

 attained their object in the discovery of new planets in the 

 most brilliant manner, as up to the present time (1850) 

 they have been the principal, though not the exclusive, 

 means of the discovery of seven new planets. ( 189 ) Of the 

 24 sheets which are to represent the heavens within 

 15 degrees on either side of the Equator, our Academy has 

 now published 16. They contain, as nearly as possible, all 

 stars clown to the 9th, and partially down to the 10th 

 magnitudes." 



I may here introduce a notice of the approximate estima- 

 tions which have been hazarded respecting the number of 

 stars in all parts of the heavens which may be visible to 

 human eyes, aided by our present powerful space-penetrating 

 telescopes. For Herschel's 20-feet reflector, which was 



