OF NEBULA AM) CLUSTERS OF STARS. 
9 
further precision of statement other than illusory. This is the case with the greater 
part of those set down as “ R. novae.” 
Column 6 contains the precession, in seconds and decimals, in R.A. for 1880 # 0. 
Column 7 contains the number of observations in R.A. which have been actually used 
in concluding the R.A. for 1830, from which that for 1860 has been computed. In all 
cases (unless where the contrary is especially indicated in a note, or otherwise as by the 
letters B. A.C. or A.S.C., Au., &c. inserted in place of a number in the column itself — which 
indicate that the R.A. is that of a star in one of those catalogues, or rests upon that 
other authority), the observations used for all objects included in my former catalogues 
are brought up from the data there registered, to the exclusion of all others ; and in 
such cases (the vast majority) no parenthesis or other distinctive mark is applied. When, 
however, no satisfactory R.A. is there recorded, or when the R.A. is there expressly 
stated to have been set down from the “working list,” the R.A. adopted is that brought 
up from the Zone Catalogue of C.H., and in such cases the number of observations 
used is enclosed in parentheses ( ). Dots attached (:) indicate some uncertainty in the 
R.A. ; (::) a very considerable doubt, extending, perhaps, to a whole minute; \ and T* 
express still wider limits of uncertainty. In those nebulae of my Father’s catalogues 
which have no number corresponding in column 2 (indicating the absence of any obser- 
vations of my own), the places set down both in RA. and Declination are those brought 
up from the Zone Catalogue of Miss C. H., and the numbers of observations on which 
they rely are set down in the appropriate column without any parenthesis or distinctive 
marks, the absence of any number in column 2 being a sufficient indication. In the 
case of M. D’Arrest’s nebulae, the numbers in column 6 enclosed thus [ ] indicate the 
number of his observations of the nebula employed by himself to give the place. 
Columns 8, 9, and 10 contain, in like manner, the North Polar Distance for 1860, the 
precessions for 1880, and the numbers of observations used for P.D. in the case of each 
object; and the same remarks apply to these as to columns 5, 6, and 7. 
In column II is given a short description of the nebula or cluster in abbreviated 
words, made out from an assemblage and comparison of all the descriptions of each 
object given in my Father’s and my own observations. As regards the former, recourse 
was had, not to the printed account in the Philosophical Transactions (which gives only 
a single description), but to a series of manuscript sheets in the nature of a Register 
(and as such cited in the notes which follow this Catalogue), into which have been trans- 
cribed, verbatim , from the original sweeps, all the descriptive parts of each and every 
observation of each cluster or nebula in the order of their dates, and the data for com- 
puting their places, derived from the sweeps by applying the index and clock correc- 
tions pertaining to each. In this Register the nebulae are entered, each with its class 
and number, and each on a separate sheet ; the whole series being arranged, however, 
not in the order of their classes and numbers, but in the order of the dates of their 
discovery, from No. 1, corresponding to October 28, 1783, to No. 2508, corresponding to 
September 30, 1802. Of these, the first 2500 only are included in the catalogues com- 
mdccclxiy. c 
