abandon the idea that all nebulosity is due to multitudes of stars.

To the inhabitants of the nebula of the present catalogue (he writes in 1786) our sidereal system must appear either as a small nebulous patch; an extended streak of milky light; a large resolvable nebula; a very compressed cluster of minute stars hardly discernible; or as an immense collection of large scattered stars of different sizes. And either of these appearances will take place with them according as their own situation is more or less remote from ours.'

During these years Herschel's observing activity was at its highest. In 1789 a catalogue of a second thousand nebulæ appeared, and then for a while, on the completion of the great telescope, the sweeps for nebulæ were laid aside. The discovery of Saturn's sixth and seventh satellites, and the long series of measures consequent on this discovery, absorbed him for a year; in 1791 he returned to the nebula with a fresh mind, and immediately there comes a result of capital importance which marks the turning-point of his views. He discovered a star of about the eighth magnitude surrounded with a faintly luminous atmosphere of considerable extent. The paper in which this is announced, 'On nebulous stars, properly so 'called,' exhibits in perfection Herschel's masterly lucidity in the discussion of his material. The new object appears to be of a very instructive nature such as may lead to important inferences. He reviews the steps by which he has passed from the Milky Way, consisting entirely of stars, to clusters in which the stellar points were smaller, yet still clearly distinguishable, and so to nebulous spots in which no trace of a star could be seen. But then the gradations from the former to the latter were by such well-connected steps as left no room for doubt that all these appearances were occasioned by stars.

'When I pursued these researches I was in the situation of a natural philosopher who follows the various species of animals and insects from the height of their perfection down to the lowest ebb of life; when, arriving at the vegetable kingdom, he can. scarcely point out to us the precise boundary where the animal ceases and the plant begins; and may even go so far as to suspect them not to be essentially different. But recollecting himself, he compares, for instance, one of the human species to a tree, and all doubt upon the subject vanishes before him. . . . A glance like that of the naturalist, who casts his eye from the perfect animal to the

perfect vegetable, is wanting to remove the veil from the mind of the astronomer. The object I have mentioned above, is the phænomenon that was wanting for this purpose. View, for instance, the nineteenth cluster of my sixth class, and afterwards cast your eye on this cloudy star, and the result will be no less decisive than that of the naturalist we have alluded to. Our judgment, I may venture to say, will be, that the nebulosity about the star is not of a starry nature.'

The star is involved in a shining fluid, of a nature totally 'unknown to us.' Granting the existence of such a fluid, he asks himself if it may not exist apart from stars? Has it been too hastily surmised that all milky nebulosity, of which there is so much in the heavens, is owing to starlight only? Can one not explain the Orion nebula much better by this luminous fluid than by the clustering of stars at a distance? Seventy years afterwards Huggins' spectroscope showed that these milky nebulæ are gaseous.

Within the limits of a review it is not possible to follow out in detail the change that came over Herschel's opinions when he had passed the turning-point of the year 1791. For a time he wrote little on the construction of the heavens. Then in 1802 he published the final catalogue of new nebulæ and clusters; and it is to be noticed that after 1790 he observed very few clusters. The short introduction to this concluding section is important for its indications of gradually changing opinions.

'Though our sun, and all the stars we see, may truly be said to be in the plane of the milky-way, yet I am now convinced, by a long inspection and continued examination of it, that the milky-way itself consists of stars very differently scattered from those which are immediately about us.' Or again: The stars of which it is composed are very unequally scattered, and shew evident marks of clustering together into many separate allotments.'

The 'sweeps' were now finished. From the year 1802 Herschel devoted his nebula nights, when the moon was absent, to the critical examination of the more important objects that had passed before him rapidly in the strenuous hours of sweeping. In 1811 he published a paper which is, in our opinion, the most masterly of all his works: Astronomical 'Observations relating to the construction of the Heavens, 'arranged for the Purpose of a Critical Examination. . . .'

With the expertise of a collector at his cabinet, Herschel

selects and arranges his objects, turns them over and criticises them, marks this as a perfect example of its class, and that as doubtful, perhaps spurious. His unrivalled familiarity with the appearance of each object in the collection gives to his catalogue raisonné an authority as yet not seriously challenged. During the century that has passed since this paper of 1811 was written the spectroscope has divided the nebulæ into gaseous and apparently non-gaseous categories; photography has given us nebula pictures of wonderful beauty, marvellous intricacy of form. Lord Rosse's discovery of the spiral form of a few nebula has been followed by the striking, though not yet fully substantiated, proposition that the greater part of the nebulæ are spirals. Barnard's exquisite pictures of the Milky Way have revealed to us the importance of the star clouds and the vast extent of the milky light in the regions affected with nebulosity. Yet there is no modern work whatever that has any pretensions to rival Herschel's careful classification and discussion in his paper of 1811. The fact is so remarkable that we must venture on a short examination of its cause.

Our theory, which may appear at first sight paradoxical, is this: The trouble is due to the General Catalogue of Nebulæ,' published by Sir John Herschel in 1864, and to the more modern 'New General Catalogue of Nebula and Clusters of Stars,' published in 1890 by the distinguished astronomer and scholar who has edited the Collected Papers. We shall not be suspected of wishing to minimise the value of the second indispensable work, the most widely used of all the publications of the Royal Astronomical Society. But we believe that this catalogue has had an unforeseen and unfortunate effect. In it every nebula known up to the end of the year 1887 is given a single line, a number, a position, and a shorthand description. Since its publication we have remarked a strong tendency to suppose that when you have allowed a nebula to have an N.G.C. number and a place in the sky, you have done everything for it that may reasonably be expected. First there comes the nebula cartographer who works on the principle: one nebula, one spot on the chart. Later there comes the wielder of modern statistical apparatus, who says in effect: Here is a jolly lot of figures very nicely arranged to save us the trouble of any enquiry into their meaning; let us analyse them into half a

dozen orders of spherical harmonics, and we shall discover laws of nature which would never have been visible to the oldfashioned cartographer, and how much less to a man like Herschel who worried himself with the individuality of each object as if it had a character and personality of its own.

There is a real danger that these modern statistical enquirers may, as Artemus Ward puts it, 'throw so much darkness on 'the subject that we shall soon know nothing about the 'early Saxons,' or other subjects of enquiry. A pioneer of modern statistics has proved that all the skulls of a certain Egyptian collection belonged to a single race of people; the anatomist replies pathetically: I cannot understand your mathematics, but if you look at the skulls you can see that they belong to two distinct races. The mathematician constructs an expression to represent the relief of the Earth's surface; the geomorphologist is respectfully doubtful about the propriety of squeezing new mountain ranges and old ocean beds into a single formula.

In all such enquiries there is need for a personal critical faculty which is beyond the realm of statistics. The scenery and construction of the heavens are as characteristic, as locally complex and significant, as the scenery and the condition of diverse regions of the Earth. For a century past astronomy has had specialists who have developed their own special branches of enquiry to an extraordinary degree, but the man has not yet appeared who can write a natural history of the sky as Herschel did for his time.

A. R. HINKS.

THE FIRST OF THE FENIANS

I. The Autobiography of Wolfe Tone. New Edition. Edited, with an introduction, by BARRY O'BRIEN. T. Fisher Unwin. 1912. 2. The Life of Theobald Wolfe Tone. By HIMSELF. Washington. 1826.

3. Studies in Irish History and Biography. By C. L. FALKINER. Longmans, Green and Co.

1902.

4. The History of Ireland in the Eighteenth Century. By W. E. H. LECKY. Longmans, Green and Co.

5. Leaders of Public Opinion in Ireland.

Longmans, Green and Co. 1871.

1892.

By W. E. H. LECKY.

6. The English in Ireland in the Eighteenth Century. By J. A. FROUDE. Longmans, Green and Co. 1872.

7. The United Irishmen. By R. R. MADDEN. James Duffy. Dublin. 1846.

8. The Cornwallis Correspondence. John Murray. 1859. 9. Howell's State Trials.

A

PECULIAR interest always attaches to the autobiographical in literature, more especially when it takes the form of a private journal written without any view to publication, and only destined for the edification of a small circle of intimates. The autobiographer, as Sir Leslie Stephen once pointed out, has ex officio two qualifications of supreme importance in all literary work: he is writing about a topic in which he is keenly interested, and on which he is the highest living authority. After reading the unwieldy volumes which the son of Theobald Wolfe Tone compiled from the vast mass of his father's personal memoranda and literary remains, it is not difficult to understand why the Duke of Wellington should have declared to Samuel Rogers that he had seldom found any book so fascinating as the diary of his brilliant but unfortunate fellow-countryman. Not only do Tone's journals supply a complete and graphic picture of the stirring times in which he lived; they also provide a minute and vivid portrait of their author, forming a fragment of ruthless self-revelation, in which the soul of the man is laid bare with an almost painful lack of self-consciousness and with a degree of candour that could never have been attained by any outside biographer.

VOL, CCXVI, NO. CCCCXLII.