140 HERSCHEL AND HIS WORK 



slowly feeling their way to a fuller knowledge of the 

 "white clouds" they were discovering among the 

 stars. La Caille, when working at a catalogue of 

 about ten thousand stars in South Africa, set down the 

 places of forty-two, which he saw in the telescope. 

 He divided them into three classes ; fourteen in which 

 there was no appearance of stars ; fourteen which were 

 clearly composed of small stars ; and fourteen which 

 combined the characters of both these classes, small 

 stars surrounded or attended by white spots. His 

 labours were published in 1755. Herschel followed at 

 the end of the century, vastly extended our know- 

 ledge of these singular objects, and completed the 

 classification which the Frenchman began. 



Turning his attention to the broad band of light 

 known as the Milky Way, of which the various 

 nebulae " seemed to be portions, spread out in different 

 parts of the heavens," Herschel at once solved the 

 puzzle that then divided the astronomical world, Is 

 it the diffused light of innumerable stars, or a shining 

 gas ? He describes it as beyond doubt " a most 

 extensive stratum of stars of various sizes " ; and 

 " that our sun is actually one of the heavenly bodies 

 belonging to it is as evident." These were two steps 

 forward, but he did not stop with them. He examined 

 that shining zone in all directions with a powerful 

 telescope a 20 - feet reflector piercing to the 

 borders of its length, breadth, and thickness. He 

 even undertook to count the number of stars he 

 saw. He called this census of stars gauging the 

 heavens. Four years afterwards, he called it analys- 

 ing them, and spoke of his method as " perhaps the 

 only one by which we can arrive at a knowledge 



