PHILOSOPHICAL TRANSACTIONS. 
I. Catalogue of Uebulae and Clusters of Stars. 
By Sir John Frederick William Herschel, Bart., F.B.S. 
Received October 16, — Read November 19, 1863. 
Introduction. 
The study of the Nebulae has, within the last quarter of a century, attracted much more 
of the attention of observers than heretofore — as well on account of the singularity of 
the phenomena presented by many of these objects, as in consequence of the increased 
optical power of the telescopes which the skill and industry of modern inventors and artists 
have placed within their reach. The brighter nebulae cannot be viewed to any advantage, 
and the fainter cannot be seen at all, except by the aid of telescopes of large aperture ; 
and, thanks to the exertions of Lord Rosse, Mr. Lassell, Messrs. Nasmyth and De la 
Rue in England, and Messrs. Steinheil, Foucault, and Porro in Germany and France, 
as regards reflecting telescopes, and to those of Fraunhofer, Merz, Cauchoix, Clarke, 
Cook, Secretan, Ross, and Dallmeyer as regards refractors ; instruments of abundantly 
sufficient optical capacity not only to repeat and verify the earlier observations, but to 
disclose new and more interesting features in many cases, have now come into the hands 
of many observers, both professional astronomers and amateurs, and may be had by any 
one who is willing to incur a cost which may be considered moderate when it is remembered 
that instruments of similar dimensions and goodness could not be obtained fifty years 
ago at any price. In consequence we find a continually increasing attention directed to 
this department of astronomy. Not to insist on the observations of the Earl of Rosse 
and Mr. Lassell with their transcendent reflectors, we find a systematic examination and 
review of them undertaken by M. D’ Arrest in the year 1855, by the aid of a refractor 
of 6-feet focal length and 4^ inches aperture in the Leipzig Observatory, whose results, 
consisting in the carefully determined places, by repeated observations, of about 230 
nebulse, were published in 1856, in a work entitled “ Resultate aus Beobachtungen der 
Nebelflecken und Sternhaufen” (Erste Reihe, Leipzig). This review has since been 
carried on by the same excellent astronomer, with the great refractor by Merz of 
11 inches in aperture and 16-feet focus, erected in the year 1861 at the Royal Observa- 
MDCCCLXIV. b 
