Hampstead, January 9th, 1851.
My dear Mary Somerville, whom I am proud to call my friend, and that she so calls me. I could say much on this point, but I dare not. I received your letter from Mr. Greig last night, and thank you very gratefully. If my head were less confused I should do it better, but the pride I have in thinking of you as philosopher and a woman cannot be exceeded. I shall read your letter many times over. My sister and myself at so great an age are waiting to be called away in mercy by an Almighty Father, and we part with our earthly friends as those whom we shall meet again. My great monster book is now published, and your copy I shall send to your son who will peep into it, and then forward it to yourself. I beg to be kindly and respectfully remembered to your husband; I offer my best wishes to your daughters....
Yours, my dear Friend,
Very faithfully,
Joanna Baillie.
My sister begs of you and all your family to accept her best wishes.
FROM SIR JOHN HERSCHEL TO MRS. SOMERVILLE.
18th March, 1844.
To have received a letter from you so long ago, and not yet to have thanked you for it, is what I could hardly have believed myself—if the rapid lapse of time in the uniform retirement in which we live were not pressed upon me in a variety of ways which convince me that as a man grows older, his sand, as the grains get low in the glass, slips through more glibly, and steals away with accelerated speed. I wish I could either send you a copy of my Cape observations, or tell you they are published or even in the press. Far from it—I do not expect to "go to press" before another year has elapsed, for though I have got my catalogues of Southern nebulæ and Double stars reduced and arranged, yet there is a great deal of other matter still to be worked through, and I have every description of reduction entirely to execute myself. These are very tedious, and I am a very slow computer, and have been continually taken off the subject by other matter, forced upon me by "pressure from without." What I am now engaged on is the monograph of the principal Southern Nebulæ, the object of which is to put on record every ascertainable particular of their actual appearance and the stars visible in them, so as to satisfy future observers whether new stars have appeared, or changes taken place in the nebulosity. To what an extent this work may go you may judge from the fact that the catalogue of visible stars actually mapped down in their places within the space of less than a square degree in the nebula about η Argus which I have just completed comprises between 1300 and 1400 stars. This is indeed a stupendous object. It is a vastly extensive branching and looped nebula, in the centre of the densest part of which is η Argus, itself a most remarkable star, seeing that from the fourth magnitude which it had in Ptolemy's time, it has risen (by sudden starts, and not gradually) to such a degree of brilliancy as now actually to surpass Canopus, and to be second only to Sirius. One of these leaps I myself witnessed when in the interval of ceasing to observe it in one year, and resuming its observation in two or three months after in the next, it had sprung over the heads of all the stars of the first magnitude, from Fomalhaut and Regulus (the two least of them) to α Centauri, which it then just equalled, and which is the brightest of all but Canopus and Sirius! It has since made a fresh jump—and who can say it will be the last?
One of the most beautiful objects in the southern hemisphere is a pretty large, perfectly round, and very well-defined planetary nebula, of a fine, full independent blue colour—the only object I have ever seen in the heavens fairly entitled to be called independently blue, i.e., not by contrast. Another superb and most striking object is Lacaille's 30 Doradus, a nebula of great size in the larger nubicula, of which it is impossible to give a better idea than to compare it to a "true lover's knot," or assemblage of nearly circular nebulous loops uniting in a centre, in or near which is an exactly circular round dark hole. Neither this nor the nebula about η Argus have any, the slightest, resemblance to the representations given of them by Dunlop.... As you are so kind as to offer to obtain information on any points interesting to me at Rome, here is one on which I earnestly desire to obtain the means of forming a correct opinion, i.e., the real powers and merits of De Vico's great refractor at the Collegio Romano. De Vico's accounts of it appear to me to have not a little of the extra-marvellous in them. Saturn's two close satellites regularly observed—eight stars in the trapezium of Orion! α Aquilæ (as Schumacher inquiringly writes to me) divided into three! the supernumerary divisions of Saturn's ring well seen, &c., &c. And all by a Cauchoix refractor of eight inches? I fear me that these wonders are not for female eyes, the good monks are too well aware of the penetrating qualities of such optics to allow them entry within the seven-fold walls of their Collegio. Has Somerville ever looked through it? On his report I know I could quite rely. As for Lord Rosse's great reflector, I can only tell you what I hear, having never seen it, or even his three feet one. The great one is not yet completed. Of the other, those who have looked through it speak in raptures. I met not long since an officer who, at Halifax in Nova Scotia, saw the comet at noon close to the sun, and very conspicuous the day after the perihelion passage.
Your account of the pictures and other deliciæ of Venice makes our mouths water; but it is of no use, so we can only congratulate those who are in the full enjoyment of such things.