ao Mr. Herschel’s and Mr. South’s observations of the apparent 
epoch, in computing which, each single measure (unless the 
contrary is expressly mentioned) is supposed to have the 
same weight : and, 2dly, a brief statement of all the results 
obtained by other observers, as far as they are known to us, 
arranged in the order of their dates, for the sake of comparison 
with our own, so as to give, as it were, a history of all that is 
known on the subject. Among them, a multitude of hitherto 
unpublished observations of Sir W. Herschel are inserted 
from his Journals and Registers ; many lacunas in the history 
of particular stars filled up, and the chain of observation 
continued unbroken up to the present time. One or two 
points here require notice, ist. The dates of his observa- 
tions will generally be found to differ from those attached 
to the description of the stars in his Catalogues. The reason 
is, that the dates here given are those of the observations, as 
they occur in the Journals, or their mean, if more than one, 
while the dates in the Catalogues are those when the stars 
were first discovered to be double. 2dly, Both the angles and 
distances will also be frequently at variance with those printed 
in Sir William’s Catalogues. This must be explained 
more at large. Unless a mean result is expressly men- 
tioned, the angles and distances in his Catalogues are in- 
variably the results of single measures. However nume- 
rous the measures taken, one has been selected as the best, 
and all the rest rejected. So great a degree of confidence in 
single measures, however, is hardly borne out by our expe- 
rience ; and the results we have inserted from the Journals 
and Registers, are therefore the means of all that could be 
found, such only being rejected as offer something obviously 
objectionable. We have only to cast our eyes at the obser- 
