that this ocean of ether is in any degree impervious to light. His friend Dr. Olbers, of Bremen, suggested that it might be. Precisely as the glass or the horn, through which rays of light pass, keeps part of them back or absorbs them, the infinite ocean of ether may have a similar effect, though in a vastly less degree. This apprehension remains a mere speculation to this day. Sometimes these islands of stars were broken into clusters of stars showing magnificent colours, and forming the most splendid objects that can be seen in the heavens. They seemed to concentrate round a centre. The Milky Way is one of these islands, of which the population consists in suns and worlds. Others, separated from it and from each other, and even apparently changing their shape from age to age, are "generally seen upon a very clear and pure ground without any star near them that might be supposed to belong to them." With all this sublimity of exposition and explanation, Herschel at the same time asks for consideration from critics and readers, "for, this subject being so new, I look upon what is here given partly as only an example to illustrate the spirit of the method."
The idea Herschel formed and then figured of the shape of the Milky Way may be best understood by comparing it to the palm of the hand with only two fingers—the middle and the forefinger—and these stretched fully out. Our sun he supposed to be near the roots of the fingers, looking out into open space through the interval between them. He had the idea also that our star-island "has fewer marks of antiquity upon it than the rest." He believed that its stars "are now drawing towards various secondary centres, and will in time separate into different clusters so as
