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ART. I.-Results of Astronomical Observations made during the Years 1834, 5, 6, 7, 8 at the Cape of Good Hope; being the completion of a Telescopic Survey of the whole Surface of the Visible Heavens, commenced in 1825. By Sir John F. W. Herschel, Bart., K.H., &c. 4to., 1847.


THIS volume is very unlike the majority of those records of Astronomical Observations which form an annually increasing load upon the quarto shelves of our scientific libraries. These may be, and for the most part are, of the greatest value, as containing the data upon which the future progress of one large department of astronomy is to be founded, but Sir John Herschel's work is a record of that Progress itself.

Practical astronomy is naturally divided into two branches :1st, that which depends mainly or solely upon the perfection of the Telescope as an instrument of research-in which the highest resources of optical art are expended in the examination of the heavenly bodies considered singly, or in such small groups as may be discerned at one time in the field of a telescope ;-2nd, that which depends more directly upon our power of measuring and subdividing time and space, whereby the relative places of the heavenly bodies are determined, the laws of their motions and the forms of their orbits: the divided circle and the clock are the characteristic implements of this branch of astronomy; telescopes of enormous power are, generally speaking, inapplicable to it. Now the bulk of the publications issuing from our national observatories belong to the latter class of inquiries; whilst the former has, with some exceptions, been left chiefly in the hands of amateurs, or at least of private individuals. The labours of Sir William Herschel, to which his son has in the present and in former works so largely added, belong in a peculiar manner to the first class. The telescope is almost the sole apparatus: fine telescopes, and the much rarer qualification of using them to the best advantage, are the requisites for success.

It will readily be apprehended that telescopic astronomy, and the records of telescopic observations, are of far more general interest than the reading of altitude and azimuth circles, the

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counting of pendulum beats, and the determination of a few seconds of error in the tabular places of a planet. And though, as we shall see, there is a vast amount of numerical work in Sir John Herschel's pages, yet the results are so numerous and varied, so striking by reason of their novelty, and so picturesque in their details, that they are fitted to interest every one who is even moderately acquainted with the general facts of astronomy, and render the work eminently readable, which is precisely what (it may be stated without any disparagement to our regular observatory publications) the others are not. The difference may be illustrated by two descriptions of a distant country which we can never hope to visit. The one is a statistical report of its extent and resources, the number of acres of arable, pasture, or wood, the latitude and longitude of its cities, the altitude of mountains, the number of inhabitants, and the sum of revenue. The other is a graphic description of its natural features and political condition; the road-book of a traveller who has explored its recesses with the eye of a naturalist and a painter, whose sketches live in our remembrance, and by an appeal to universal associations, enable us to realize scenes and manners which we shall never see for ourselves, but which we learn to compare with what has been all our life long familiar. Thus does the astronomy of the telescope lead us to understand in some degree the economy of other systems; it brings to its aid every branch of physical science in order to obtain results regarding the nature and changes of distant worlds, and to enable us to interpret these results aright by the analogies of our own.

The title-page of Sir John Herschel's book explains its nature and importance: it records 'the completion of a telescopic survey of the whole surface of the visible heavens, commenced in 1825.' The grave had not closed for three years over his illustrious Father, when the Son proceeded to carry out and complete, by rare sacrifices, the course of observation in which for half a century Sir William had no rival; and by extending the survey to the southern hemisphere, he rendered compact and comparable one of the most elaborate inquisitions of nature which two men ever attempted.

Sir John Herschel's position and attainments fitted him admirably for so great a work, and justly entitle him to the unenvied position which he now holds amongst the cultivators of exact science. Bearing a name honoured and revered by all, his career at Cambridge reflected upon it fresh lustre; the variety and extent of his acquirements gave him a reputation amongst his college contemporaries, afterwards fully confirmed by the not more impartial voice of mankind at large. Since that time he


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