[glenc (Glen)]

John Herschel wrote:
“Of the objects remaining, 135 are nebulae and clusters of my Father's catalogues, now, for the first time, re-observed; 9 are Messier's, 5 of which are identical with objects catalogued by Mr. Dunlop; and 206 others have also been identified, with more or less certainty (indicated by the absence or presence of the sign ?), with objects observed by Mr. Dunlop, and described in his Catalogue of Nebulae. The rest[1] of the 629 objects, comprised in that catalogue, have escaped my observation; and as I am not conscious of any such negligence in the act of sweeping as could give rise to so large a defalcation, but, on the contrary, by entering them on my working lists (at least, until the general inutility of doing so, and loss of valuable time in fruitless search, thereby caused it to become apparent), took the usual precautions to ensure their rediscovery; and as I am, moreover, of [the] opinion that my examination of the southern circumpolar region will be found, on the whole, to have been an effective one, I cannot help concluding that, at least in the majority of those cases, a want of sufficient light or defining power in the instrument[2] used by Mr. Dunlop, has been the cause of his setting down objects as nebulae where none really exist. That this is the case, in many instances, I have convinced myself by careful and persevering search over and around the places indicated in his catalogue.”[3]

[1] 418 objects = 66.5%
[2] The original footnote says, “A 9-inch Newtonian reflector, of 9 feet focal length, which, in point of light, would correspond to about one-seventh of that used in my [John Herschel] sweeps. That such was its construction, I conclude from the mention of the large mirror in Philosophical Transactions, 1828, p.113.”
[3] J. Herschel, Astronomical Observations, p. 3.