I delayed acknowledging it till I could inform you at the same time I had seen it. The frost, unfortunately for us astronomers, broke up the very same morning that your letter arrived, in consequence of which the weather has been so bad that I could not get a sight of your comet till last night, the 26th, when, at 6^h 34ʹ, it followed α Lyræ in the A. R., 3ʹ 7ʺ of time, and was 2° 30ʹ S. of it. This only by the divisions of the equatorial and meridian circles, but true to a minute or two of declination and five seconds of time. I compared it more accurately with a small telescopic star nearer it, which, when settled hereafter, will determine its place within 30ʺ of a degree. Hence its A. R. was about 18^h 33ʹ 55ʺ, and distance from the North Pole 53° 59ʹ. By your observation of December 22nd, 5^h 31ʹ in the morning, its A. R. was 18^h 35ʹ 12ʹ, and P. D. 56° 56ʹ. Hence it has moved retrograde in A. R. about the rate of 17ʹ of time per day, and 30ʹ per day northward in declination, which agrees nearly with your observation of its approach towards δ Lyræ. Its motion is fortunately favourable for our keeping sight of it for some time, which may be very useful, especially if it should be moving from us, which there is an equal chance for, as the contrary. It appeared to me very faint, and rather small, but the air was hazy. By its faintness and slow motion, it is probably at a considerable distance from the earth. Time will explain these things. Let us hope the best, and that it is approaching the earth to please and instruct us, and not to destroy us, for true astronomers have no fears of that kind. Witness Sir Harry Englefield’s valuable tables of the apparent places of the Comet of 1661, expected to return at this time, with a delineation of its orbit, who, in page 7, speaks of the possibility of seeing a curious and beautiful transit of it over the sun’s disk, should the earth and comet be in the line of the nodes at the same time, without _horror_ at the thought of our being involved in its immense tail. I would not affirm that there may not exist some astronomers so enthusiastic that they would not dislike to be whisked away from this low terrestrial spot into the higher regions of the heavens by the tail of a comet, and exchange our narrow uniform orbit for one vastly more extended and varied. But I hope you, dear Miss Caroline, for the benefit of terrestrial astronomy, will not think of taking such a flight, at least till your friends are ready to accompany you. Mrs. Maskelyne joins me in best compliments to yourself and Dr. and Mrs. Herschel. If your observation was precise as to the difference of A.R. of the comet and β Lyræ, it may be of use for determining the orbit, especially if the comet should be going off from us. I have not yet examined whether it can be the French comet discovered by M. Messier, on the 26th of last month, which was going from the earth. Its apparent motion must have turned at right angles to its former one,