have followed in his footsteps with a better equipment of instruments, if not with a richer endowment of insight or genius. Others still have looked upon his lifelong quest as an attempt to reach the foot of the rainbow ladder, or to master the secret of the philosopher's stone. His papers remain a wonderful monument of ingenious research and marvellous discovery, of lofty imaginings and reasoned conclusions.
These nebulæ and clusters of stars Herschel called milky ways, different from the great Milky Way, in which our solar system is imbedded. He held at first that they are in no respect connected with our milky way, but are star-islands or world-systems, perhaps only in process of formation, at immense distances from our sun, outlying provinces of creation, as it were, in the vast ocean of ether, or constructions only begun in the realms of space. He is supposed to have fallen from this opinion in his later years, and to have imagined that all these milky ways and star-clusters were connected with ours. His latest papers give no indication of this change of view. He appears indeed only to have changed his view in so far as to have regarded our milky way as the greatest of all the milky ways, visible in our telescopes: but on this point he was scarcely justified in speaking, as the distance of the nearest nebula not only was and continues to be unknown, but the means of determining the distances of these white clouds have not yet been discovered. It is thought that the great nebula in Orion, if not the nearest to us, is among the nearest. Herschel maintained this. He had some grounds also for believing that changes had taken place in the positions of the nebulous matter during the thirty-seven years he
