MISS HERSCHEL TO J. F. W. HERSCHEL.
Feb. 1, 1826.
My dearest Nephew,—
On the 17th January I received by the same post your letters of December 30th and January 9th. I should have answered your precious communication of December 30th immediately if I was not in hopes of receiving daily an answer to what I sent on the 28th December. I cannot express my thanks sufficiently to you for thinking me worthy of forming any judgment of your astronomical proceedings, and am only sorry that I cannot recall the health, eyesight, and vigor I was blessed with twenty or thirty years ago; for nothing else is wanting (and that is all) for my coming by the first steamboat to offer you the same assistance (when sweeping) as, by your father’s instructions, I had been enabled to afford him. For an observer at your twenty-foot when sweeping wants nothing but a being that can and will execute his commands with the quickness of lightning [!], for you will have seen that in many sweeps six or twice six, &c., objects have been secured and described within the space of one minute of time.
I cannot think that any catalogue but the MS. one in zones (which was only intended for your own use) would facilitate the reviewing of the Nebulæ, and you are the only one to whom 1885, viz., 2nd and 3rd class, out of the 2500, can be visible in your twenty-foot. Wollaston, who knew this, has given in his Catalogue only 1st and 4th, &c. classes of the first 1000, the second not having been published at that time, and they are without the yearly variation.
Bode has given the first and second Catalogues complete, and calculated the yearly variation to each by de Lambre’s Tables. (See Bode’s preface, p. iv., line 18.) The last 500 were not published yet in 1800, or rather 1801. I only mention this that if you wanted the variations, and had a mind to trust to that catalogue of errors, it would save an immense trouble by copying them. But the more I think of these, the more I doubt if it would not be injuring the places of objects merely (though accurately) pointed out, to calculate them in the same manner as stars repeatedly observed in fixed instruments; and I doubt if your father noticed Bode’s having done so.
You will find undoubtedly many more nebulæ which may have been overlooked for want of time, flying clouds, haziness, &c., especially in those sweeps which are registered half sweep. It is a pity time could not be found for making, as was often intended, a register in which the boundaries of the sweeps, with the nebulæ, were all brought to one time, either to Flamsteed’s or 1790 or 1800. The register in Flamsteed’s time, which is from 45° to 129°, is for that reason the best mem. At the time that register was made, the apparatus for sweeping in the zenith was not completed, and higher than 45° was not used.
If you should wish in the latter part of the summers (when your father was generally from home) to fill up the unswept part of the heavens, you might perhaps discover as many objects as would produce a pretty numerous catalogue. You will see in the register of Flamsteed’s time a curved line which denotes that the Milky Way is in those places, and if you see an L and find a cluster of stars thereabout, I shall claim it as one of those I mentioned in my last letter to you. It was the assistant’s business to give notice when such marks or any nebulæ in the lapping over of the sweep either above or below were within reach, by making the workman go a few turns higher or lower. (N.B. No more than is convenient without deranging the present sweep.) But I am forgetting myself, and fear I am tiring you unnecessarily, and will only add that if your father wanted at any time to review or to show any of his planetary or other remarkable nebulæ to his friends, the time and P.D. was, by the variation of its nearest star in Wollaston’s or Bode’s catalogue, brought to the intended time of observation, and P.D.—comp. of latitude, with allowance for refraction, gave the quadrant for setting the telescope.
But after all, dear Nephew, I beg you will consider your health. Encroach not too much on the hours which should be given to sleep. I know how wretched and feverish one feels after two or three nights waking, and I fear you have been too eager at your twenty-foot, and your telling me that you have been unwell for some months, and now only begin to feel better, makes me very unhappy, and I shall not be comfortable till I see by your next that you are perfectly well again; I am quite impatient to see what you have to say about the parallax of the fixed stars, but on such occasions I am vexed that your father did not live to know of your grand discoveries. You say something of a paper on the longitude of Paris; I hope you will think of Gauss when you have anything new.
Among the letters from your father’s correspondents in alphabetical parcels you will find under the letter P. some of Pond’s, who was about the end of the last century in Lisbon, with an excellent seven-foot telescope of your father’s, and I remember that several letters passed between them about a double star in Böotes.