photography is such that the late superintendent, Admiral Mouchez, remarked that 'at first sight a doubt might be entertained as to the accuracy of the results.'

Good photographs have also been obtained by Dr. Roberts, using a reflecting telescope of twenty inches aperture. On a plate of a portion of the Milky Way in Cygnus, taken in August, 1887, with an exposure of an hour, no less than 16,000 stars can be counted on a space of about four square degrees.

Photographs of double stars have also been taken at the Paris Observatory, and from these accurate measures of position can be obtained which will be of great value in the calculations of the orbits of these interesting systems.

To avoid the danger of accidental specks on the plates being mistaken for stars, the plan has been tried at the Paris Observatory of giving three exposures on each plate, the three images forming a small equilateral triangle, which can only be seen with the aid of a microscope. Another advantage of this method is that the time of exposure for each image may be shortened, the triple image producing a combination which is more easily seen than a single image. Should one of the minor planets between Mars and Jupiter happen to be present in the region photographed, it could at once be detected by the distorted shape of the small triangle; and it is believed that even a planet beyond Neptune might be detected in this way. If a trans-Neptunian planet exist it will probably be discovered by photography. Several of the minor planets have already been discovered by this method.

For the fainter stars, however, an exposure of one hour is necessary for each image, and the continuous exposure of three hours required for the triple image is a great strain on the observer's eye and patience, and forms a serious objection to the general adoption of this plan. By the use of more sensitive plates and larger telescopes, the time of exposure will probably be considerably reduced in the future. When examined with a microscope, however, the appearance of the stellar images is so peculiar that accidental spots can be easily distinguished. With a high power the images look like globular clusters of stars as seen in a telescope, and they have been described as resembling 'a heap of shingle.' For this reason a single exposure will probably be adopted in constructing a chart of the heavens.

In the year 1887 an International Conference of astronomers was held at Paris, for the purpose of arranging the details of a

The

photographic chart of the whole heavens on a uniform plan. Conference was composed of fifty-six astronomers, representing sixteen different nations. It was resolved that refracting telescopes of about thirteen inches aperture should be used in the work. A series of plates will first be taken showing stars to the eleventh magnitude. From these a catalogue will be formed, which will serve as a foundation and reference for all similar work in the future. This catalogue will, it is supposed, include about one and a half million of stars. A second set of plates will also be obtained showing stars to the fourteenth magnitude inclusive, and these will probably contain about twenty millions of stars.

Another congress was held in Paris in September, 1889, when further details were considered and arranged.

The work will be divided among a number of observatories in different parts of the world, and already some progress has been made in the construction of the necessary telescopes and the carrying out of the plan, which, it is hoped, will be brought to a successful conclusion before many years have elapsed.

Some remarkable results have already been obtained by photography. The satellites of Mars and Neptune, and Saturn's rings have been photographed. Photographs of the great Orion nebula by Drs. Common and Roberts show a great extension of this wonderful object. The great nebula in Andromeda, the spiral nebulæ, and others, have been successfully photographed by Dr. Roberts. In the Andromeda nebula, we see that the whole mass is breaking up into rings of nebulous matter, and the photograph suggests unmistakably the probable formation of a solar system on the lines of Laplace's Nebular Hypothesis.

Photography has also been successfully employed in the determination of stellar distances and in the study of stellar spectra. A catalogue of the spectra of over 10,000 stars, and entitled 'The Draper Catalogue,' has recently issued from the Harvard Observatory. It has been formed in honour of the late Dr. Henry Draper, and forms a fitting monument to the memory of that distinguished astronomer. An examination of the photo

graphed spectra has revealed the existence of some very close binary stars revolving in unusually short periods-double stars of which the components are so close that the largest telescopes in existence have failed to show them as anything but single

stars.

Photographs of the Milky Way have also been successfully

taken by means of a portrait lens strapped to a telescope driven by clockwork. The pictures obtained are very beautiful, and give promise of still better results in the future. The study of these and the stellar charts, when completed, will probably add considerably to our knowledge of the construction of the sidereal universe.

The preceding short sketch of the rise and progress of celestial photography will show that we may look forward in the future to a great increase of astronomical knowledge by its aid. Assisted by even larger telescopes and more sensitive plates than we now possess, the heavens will be studied in a way undreamt of by our ancestors, and, in the words of a well-known astronomer, 'the records that future astronomers will use will not be the written impressions of dead men's views, but veritable images of the different objects of the heavens recorded by themselves as they existed.'

SIX STUDIES IN ITALIAN LITERATURE.

IV.

IN the previous articles, attention was chiefly drawn to the poets, while comparatively little notice was taken of the prose writers. In the present paper it is proposed to remedy this defect, and to pass in review the principal prose authors of the period comprised between the birth of Dante and the death of Torquato Tasso. In apology for our neglect it might be urged that, as Boccaccio is acknowledged as the Father of Italian Prose, it would be superfluous, especially in a brief survey, to refer to his predecessors, whose imperfections are sufficiently attested by this title. Such a plea, however, would hardly avail. This description of Boccaccio as the Father of Italian Prose is a tribute of admiration, and, as such, must not be pressed. To make it historical, complete, an addition would be necessary, and we should have to speak, not of prose, in its wide generic signification, but of artistic prose. Prose composition, however, has other uses than the exhibition of a beautiful style. It may be employed to amuse, to edify, or to instruct, and its prime virtue, as Madame de Staël (I think) observed, is lucidity. If lucidity is to be set up as the test, then, of a surety there were prose writers, and respectable prose writers too, before Boccaccio.

Giving no more than a preliminary glance at Dante's Convito, the epistles of Fra Guittone, and the chronicles of Spinelli (or 'o') and the Malespini family, we pass at once to the earliest, and, in some respects, most interesting, of Italian historians, Dino Compagni. This admirable man was born we know not quite when, seemingly, however, about ten years before Dante; and he died, we have every reason to believe, in 1324. Like Boccaccio, Addison, and numberless other prose writers, Compagni served a sort of apprenticeship to his art by verse-weaving, in which exercise, though his verse was mainly imitative, he did very well.

After a youth spent in this way, he embarked on the sea of Florentine politics, always stormy, but never more so than at this particular epoch, when (as we have already had occasion to note) Dante, and Petrarch's father, and many worthy and excellent Florentines, who have the misfortune to be no longer interesting to anybody, were constrained to depart the city, and became, like guilty Cain, 'fugitives and wanderers in the earth.'

It is sometimes the case that persons destined to the favourable remembrance of posterity cut no figure whatever in the eyes of their contemporaries. This is true, in a modified sense, of Dante, of whom Carlyle-without large obligations to syntax, and in a strain of slight exaggeration-observes: 'An unimportant, wandering, sorrow-stricken man, not much notice taken of him while he lived.' Compagni for his part preferred the present, managing to hold his head rather high among his fellows, by whose favour he was enabled to enjoy the pride of place, and to revisit, in the same or a like capacity, the scenes of his former grandeur. He was twice Prior, once Gonfaloniere; and in what we may term la haute politique, as distinguished from the captious animosities of Blacks and Whites, he was a Ghibelline. The Ghibellines, it may be remarked, were the aristocratic, or feudal, party.

Relying on the proximate triumph (as he hoped) of the Emperor Henry, Dino Compagni, with charmed pencil, drew a sketch of contemporary Florence, its demagogic licence and manifold corruptions-a sketch so vivid that the personages almost put on flesh and blood, and the reader, like a confidential friend, is escorted behind the scenes, where everything proceeds sans façon, and there is neither mystery nor masquerade. The death of Henry and the consequent collapse of his enterprise, inducing in Dino a spirit of caution, caused him to suppress his composition; and the earliest extant copies of it date from the fifteenth century. This circumstance has excited doubts whether the history is really what it pretends, but it is now generally received as genuine.

A younger contemporary of Compagni who also devoted himself to historical studies was Giovanni Villani, the time of whose birth is not exactly known, though it certainly occurred during the second half of the thirteenth century. Villani was by profession a merchant, and he was a much-travelled man. Flanders he knew, and France, intimately, while at Florence he was several times Prior, and, besides, he had something to do