Page:Memoir and correspondence of Caroline Herschel (1876).djvu/107

Rh also of the parallel can hardly err so much as 15 seconds of a degree.

This, and several evenings afterwards, I viewed the comet again with such powers as its diluted light would permit, but could not perceive any sort of nucleus which, had it been a single second in diameter, I think, could not well have escaped me. This circumstance seems to be of some consequence to those who turn their thoughts on the investigation of the nature of comets, especially as I have also formerly made the same remark on one of the comets discovered by Mr. Mechain in 1787, a former one of my sister's in 1786, and one of Mr. Pigott's in 1783, in neither of which any defined, solid nucleus, could be perceived. 2em March 3, 1789.

The third comet was discovered on the 7th January, 1790; the fourth on the 17th April of the same year, during her brother's absence from home. It was announced to Sir Joseph Banks in the following letter:— April 19th, 1790. ,— I am very unwilling to trouble you with incomplete observations, and for that reason did not acquaint you yesterday with the discovery of a comet. I wrote an account of it to Dr. Maskelyne and Mr. Aubert, in hopes that either of those gentlemen, or my brother, whom I expect every day to return, would have furnished me with the means of pointing it out in a proper manner.

But as perhaps several days might pass before I could