constructing a catalogue of fixed stars. 407 
of the star itself ; this objection however is but trifling, 
compared with a more important one, which is this : if the 
observation of a. Aquilae be omitted, either from bad weather, 
or from its passing the meridian at an inconvenient hour, or 
from neglect, then the observations of all the other stars are, 
for the purposes of this investigation, rendered entirely useless. 
Hence arose the necessity of combining the observations of 
so many years, to construct a catalogue with the accuracy 
required. That extreme accuracy was ultimately obtained, I 
am most happy to have it in my power to affirm, since the 
difference is almost insensible between the catalogue lately 
deduced from the new transit instrument and that of my 
predecessor ; though an interval of ten years has intervened 
between the periods of their construction. The advantage 
therefore of my method I conceive to consist in this ; that a 
catalogue may be constructed from the observations of a 
single year, equal in accuracy to one which formerly was 
obtained in three. 
The method I propose is equally applicable to the mural 
circle and the transit instrument. With neither do I assume 
any particular star as a point of departure, in preference to 
the rest; but, on the contrary, every star in its turn is 
assumed as a point of reference to the others; thus endea- 
vouring, in the first instance, to establish their relative dis- 
tances from each other on the equator, or meridian, leaving 
the choice and determination of some common point of 
departure as a subject for future consideration. 
To render this more easily intelligible, perhaps it would be 
better to consider each instrument separately. 
