252 Proceedings of the Royal Society. 
desirable that a second re-examination should be instituted: ac- 
cordingly in the year 1816, some progress was made by Mr. — 
Herschel towards its accomplishment, and the results are commu- 
nicated in the present paper. A similar idea having, however, oc- 
curred to Mr, South, it was at length determined that the obserya- 
tions should be carried on in concert, and with his instruments. 
Meanwhile (unknown to the authors of this paper) a similar 
undertaking had been entered upon by a distinguished continental 
astronomer, Mr. Struve, director of the Imperial Observatory at 
Dorpat, and the general coincidence between the measures of this 
observer and those of their own, is deemed at once interesting and 
corroborative of the accuracy of both. 
The instruments with which the observations accompanying this 
paper were made, are a five and seven feet equatorial; the former 
was constructed under the direction of the late Captain Huddart, 
and is remarkable for its extreme lightness, for the promptitude 
with which it obeys its adjustments, and for its ability in retaining 
them. Its object glass 33 inches aperture, and of five feet focal 
length, is the work of the late P. and J. Dollond, whilst its divided 
circles, microscopes, &c., were completed by Messrs. I. and E. 
Troughton. A description of it is given, and a drawing is annexed. 
The latter is a telescope of seven feet focal length, and five inches 
clear aperture; it was made by Tully, and is mounted on the polar 
axis of the old equatorial sector, made for the royal observa- 
tory, and for the use of which an acknowledgment is made to 
the Council of the Society. 
The micrometers employed are the work of Mr. Troughton, and 
have long since been familiar to astronomers under the name of 
Troughton’s Wire Micrometers. The measures of distance are all 
central. The observations of each star were generally made in 
each other’s presence ; but occasionally in different parts of the 
observatory, and with different instruments, without any commu- 
nication with each other; in some instances the observations of 
Mr. Troughton or Mr. Richardson haye been appealed to, in order 
to settle discrepancies. . 
To the observations of each star the authors attach their mean 
