Royal Astronomical Society. 231 
0 = 4+20°62— 6781— 2 or O=— 4719— 2 
0 = —17°85 — 79°30-— 22 0 = — 97:15 —22 
0 = —22°40 — 124-42 —32 = —146°82 —32 
“Hence we get «= — 48711, by the substitution of which 
there result the following differences :— _ 
41°52 
+0°27 
—0°69 
of the perturbations of longitude. These differences, as well as 
those of the perturbations of the radius vector, are smaller than 
might have been expected, when we reflect on the total diversity of 
the methods employed, and the long calculations which the method of 
mechanical quadratures requires. Besides, my method is so simple 
that I am astonished at not having discovered it long ago; I have 
employed only eight days for the calculation of the preceding per- 
turbations, the general expression of which belongs to every point of 
the orbit of the comet. I have thus succeeded in solving this pro- 
blem, of which we till the present time possessed no solution. 
“I beg you to communicate this letter to the Royal Astronomical 
Society, and to the Royal Society of Sciences, and to accept the ex- 
pressions of high consideration, with which I am, Sir, 
** Your very obedient servant, 
“ Gotha, Dec. 14, 1842.” « P. A. Hansen.” 
II. On a new Arrangement of a Vertical Collimator attached to 
the Altitude and Azimuth Instrument. By W. Simms, Esq. An 
abstract of this paper will be found in the Monthly Notices for Ja- 
nuary 1843, vol. v. p. 230. 
III. Description of a Universal Instrument made by M. Ertel of 
Munich, and presented to the Society by Alexis Greig, Esq., Vice- 
Admiral in the Imperial Russian Navy. By M. Ertel. Translated 
from the German by Mr. Charles Knorre, and communicated by Ad- 
miral Greig. 
This paper commences with a detailed statement of the cautions 
to be used in taking the instrument out of its cases, and of fitting it 
up for observation; and gives minute directions for rectifying and 
using it. It is accompanied by two drawings, the first of which is 
that of a projection parallel to the plane of the horizontal circle of 
the instrument; and the second exhibits in detail some of the 
essential parts of it. 
IV. Occultations observed chiefly at Ashurst in the Year 1842. 
By R. Snow, Esq. 
V. Observations on the (apparently periodical) Variations in the 
Lustre of certain Stars of the First Magnitude. By T. Forster, Esq. 
Abstracts of the two preceding communications also are given in 
the Monthly Notices for January 1843. 
