IV. — The Comet OF 1771 : INVESTIGATION OF THE ORBIT. By 
William Beebe. 
The orbit of this comet, as computed by Encke, has an excentri- 
city of 1 ‘0093698 ; and as it was observed for more than three months 
and through a path of more than 130°, it is considered the best 
determined of all hyperbolic orbits. But an examination of Eucke’s 
work shows that this result was obtained by the use of only six of 
the large number of observations available, and that he has computed 
a parabolic orbit which satisfies the same observations, not quite as 
well as the hyperbolic it is true, but yet within very reasonable errors 
of observation. 
To render his work complete, therefore, needs a discussion of all 
the observations by the method of least squares. This discussion 
will be three-fold : 
First. To verify Encke’s work as far as that extended, by showing 
whether the whole body of observations gives the same result as six, 
when treated in the same way. 
Second. To show whether a consideration of the perturbations, 
which Encke neglected, will modify these results and how much. 
Third. Since the last and a highly important part of the observa- 
tions is subject to large errors, to show what effect will be produced 
by any reasonable variation of these observations. 
I. — The observations are as follows : 
a. Ten by Maskelyn at Greenwich, differential measurements, 
made with a telescope of thirty inches focal length mounted on an 
equatorial sector, that is, a brass arc of 6° in length for measuring 
differences of declination, placed upon a portable stand with leveling 
screws, etc., and provided with a motion parallel to the equator. 
The observations in right ascension were made over three wires, and 
the time estimated to the eighth of a second ; one measurement was 
made for difference of declination at each transit and two or three 
transits were taken over all the wires at each observation. They are 
published in the original form in Maskelyn’s Observations, vol. i, 
page 1 15 of Zenith Distances; clock rates and errors are also appended 
as well as comparison stars. As the comet had a good bright nucleus, 
these right ascensions seem about as reliable as measurements of the 
