the stars revealed by powerful telescopes there are thousands as large as Sirius, and millions as large as our Sun — all with their attendant systems speeding with inconceivable rapidity on their several courses!

I would ask, in conclusion, whether we have now better reason than the astronomers had of old time to consider the mysteries of the universe as fully revealed to us and interpreted. We know much that was unknown until of late, and we have been able to understand some matters which once seemed inexplicable; but the star-depths, as we see them now, are even more mysterious, as well as far more wonderful, than as displayed to the astronomers of old.

STAR GAUGING.

THE account of Sir W. Herschel's labours and views presented in our text-books of astronomy, is unfortunately so inexact, that the title itself of this paper will appear strange to many readers. We not only hear nothing about Sir W. Herschel's employment of two different methods of star-gauging in such treatises, but we actually find neither of his methods presented correctly, inasmuch as the properties of the two methods are assigned to a single nondescript method, the incongruities thus arising being apparently altogether overlooked. It is partly with the hope of rendering better justice to the greatest of observational astronomers than has heretofore been accorded to him, that I now write, but partly and chiefly in order to prepare the way for submitting to the notice of students of the heavens a method of research which promises to throw light on the noblest but most difficult of all the problems of astronomy, the determination of the laws according to which the sidereal universe has been constructed. It was this problem which Sir W. Herschel regarded as the end and aim of all his astronomical researches, even of those which seemed to bear little upon it. He observed other objects for practice and to test his tele

researches,-"A knowledge of the construction of the heavens," he wrote in 1811, after more than a quarter of a century of stellar study, "has always been the ultimate object of my observations."

I cannot but express some degree of surprise at the fate which has befallen the noble series of papers in which Sir W. Herschel presented his researches to the world. As I have elsewhere pointed out, little "has hitherto been done to bring the records of his labours properly before the student of astronomy. His papers, merely collected into a volume, would form a most important addition to astronomical literature; but, if suitably edited, and illustrated by the work of his son, and of others who have succeeded him in his own field of work, the volume would do more to advance the study of sidereal astronomy than any work which has been published during the last century." With very few exceptions, what has hitherto been done in making Herschel's words and work public, has been an injustice to his memory. It seems to have been supposed that his papers could be treated as we might treat such a work as Sir J. Herschel's " Outlines of Astronomy;" that extracts might be made from any part of any paper without reference to the position which the paper chanced to occupy in the complete series. Nay, it seems to have been thought a tribute of respect to his memory thus to quote his words without question or debate. The idea does not seem to have occurred to any one (with the solitary exception of Wilhelm Struve), that it is but an ill compliment to the great astronomer to

assume that he laboured from 1784 to 1818 upon a subject scarcely touched before his day, without making any such progression towards new knowledge that his earlier views had to be corrected in the light of later researches. It seems to have mattered little that he himself in so many words expressed the fact that his views had altered: he had said such and such things in 1784 and 1785; and those things the world was bound to accept as his teaching, whatever he might say thereafter to the contrary. And if anyone should express doubts as to those earlier views, and should endeavour to strengthen his position by quoting Sir W. Herschel in 1818 against Sir W. Herschel when thirty-two years younger, it was the fashion to denounce such attempts as altogether rash and presumptuous. This is as though every writer on astronomy should present Kepler's youthful fancies about the relations between the regular solids and the planetary orbits as the matured views of that astronomer, and denounce as irreverent any attempt to suggest that, on the whole, the laws of elliptic motion subsequently discovered by him were better worthy of respectful consideration.

We owe, I conceive, to French writers part of the misconception which has arisen respecting Herschel's labours. It pleased Arago to forsake in Herschel's favour the usual attitude of French men of science with respect to foreigners. He published a work, purporting to be an Analysis of Herschel's Life and Labours. In this work the earliest ideas of Sir W. Herschel respecting the con

before he had made any systematic observations whatever, —are presented with an unfortunate perspicuity. I refer to Herschel's paper of 1784, about which I shall presently have to speak more at length. It is here we find the first enunciation of the famous grindstone theory of the universe, at least the first remarks of Sir W. Herschel on that theory, for it is to Wright of Durham that the first enunciation of the theory is really due. This theory Arago presents, making use of the relations which in 1784 Sir W. Herschel expected to find. At p. 456 Arago says, "the galactic system is a hundred times more extended in one direction than in another," and he then refers to a picture of a certain solid figure illustrating Herschel's ideas in 1784 respecting the shape of our system. But as Wilhelm Struve justly remarks, the only section based on Herschel's observation (presented in the paper of 1785) shows the greatest extension as exceeding the least not in the proportion of 100 to 1, but only as 5 to 1; while the solid figure pictured in 1784 did not in any way relate to observations made by Herschel. It is not too much to say that Arago probably limited his real study of Herschel's papers to the paper of 1784, dipping into the others to gather thence the more striking passages, in full confidence that they accorded well with the views enunciated in 1784, and consequently without any attempt to understand the gradual progression of Herschel's ideas respecting the universe.

The effect of this has been disastrous. All the French writers and most of the continental writers,-Guillemin,