152 HERSCHEL AND HIS WORK 



a lofty theme, the same insight into general principles, 

 as illumined the first paper he wrote on the subject 

 thirty-five years before. Although his sun was near- 

 ing its going down, there was no loss of its morning 

 brilliance. "Of all the celestial objects consisting of 

 stars not visible to the eye," he writes, "the Milky 

 Way is the most striking. ... Its general appearance, 

 without applying a telescope to it, is that of a zone 

 surrounding our situation in the solar system, in the 

 shape of a succession of differently condensed patches 

 of brightness, intermixed with others of a fainter 

 tinge." But his latest observations led him to believe 

 that the Milky Way is a fathomless, and comparatively 

 thin stratum of stars, of which his 40-feet reflector 

 would sound the depths " to the 2300th order of dis- 

 tances and would then fail us." He imagined also he 

 had "shown how, by an equalisation of the light of 

 stars of different brightness, we may ascertain their 

 relative distances from the observer, in the direction 

 of the line in which they are seen." Among these last 

 words was his expressed conviction that the Milky 

 Way is the most brilliant, and beyond all comparison 

 the most extensive sidereal system. He thus held to 

 the end that it was one of many systems, of which it 

 bulked in his eyes as a great continent in an ocean of 

 ether, while the nebulae are outlying islands. Within 

 the bounds of the Milky Way he believed that all our 

 stars, visible to the naked eye, are contained. If an 

 18-inch globe represented all these stars, it would 

 require a line 45 feet long to be added to express 

 the distance of the 734th order of stars, and, while he 

 saw many of the 900th or 980th order, he was con- 

 vinced that his 40-feet telescope would penetrate space 



