tion, and where the position of the axis enables us to trace a circular arrangement even to the vicinity of the Poles, and to infer with little chance of error, that notwithstanding the slackened rotation, arctic and antarctic belts exist upon Jupiter also.

As to the possible extent of this atmosphere, we have little to guide us. No observer, however powerful may be his optical means, has ever recorded any deviation in the outline of the limb as it traverses successively the darker and brighter portions; and yet a considerable depth would seem to be required, to admit of a difference in the velocity of rotation between the upper and lower regions, adequate to the production of so persistent a streakiness. The fact that this streakiness affects the whiter more than the yellower parts of the disc may be significant as intimating that the yellow vapours, if such they are, are of less vertical thickness, whatever may be their relative situation in the atmosphere. I am, as before, doubtful as to the existence of any such fading of the ends of the dark stripes as might arise from imperfect transparency in their clearer air. On some occasions I have believed that the North temperate belt has been fainter towards its extremities; and on Jan. 20 I thought the falling-off much more perceptible in this than in the other belts; which, if such delicate variations at the extreme verge of optical power could be trusted, might accord with the supposition of its greater vertical depth. At other times the whole of the belts preserved their tone very fairly to their extremities; and my impression is confirmed that either optical deficiency has vitiated some previous representations, or that the condition of the planet's atmosphere has been on such occasions widely different from that which it has now long maintained.

There seems little doubt that for a considerable time the North has possessed a clearer sky than the South portion of the planet. The coincidence with the period of summer in that hemisphere will be remarked: nor need the slight inclination of the axis be considered a bar to the natural conclusion, since, when the whole constitution of the globe is evidently very unlike our own, there is nothing forced in the supposition that a slight difference of inclination might be much more influential than in our own case. At present it is a mere suggestion, arising from slender evidence, and requiring further observations for its confirmation.

The most singular feature of the disc continues to be the prevalence of these elliptical areas, which it is so difficult to explain by any terrestrial analogy. That they are not confined to the equatorial region, and in fact do not there attain their

largest dimensions, appears from the very curious object delineated by Mayer and Gledhill; while some older drawings by one of our first observers, which I have been permitted to see, prove that they have been in other seasons abundantly developed in less central latitudes. At present we seem far from any solution of this mystery, while so little of a similar character can be traced among the cloud-masses of our own skies.

It may be worth consideration whether the superior brightness of the interior of the disc might lead to any inference as to the nature of the reflecting material. It is well known that the difference, though not perceptible by the eye, is very material, as we can in no other way explain the singular change occasionally noticed in some of the satellites to chocolate-colour or even absolute blackness during the time of transit. It would be interesting to know whether this very remarkable effect of contrast has ever taken place in front of the dark belts ; more probably it has been confined to the luminous zones. Experiments might perhaps be devised which might show whether the more compact and regularly rounded of our white terrestrial cumuli exhibit any similar inequalities of luminosity, dependent on the angles of illumination and reflection. Many points of interest may probably be elucidated by other means than direct telescopic vision; and we must look forward with especial interest to the results which are, we trust, reserved for the magnificent apparatus and experienced eye of Dr. Huggins.

A comparison of the sketches taken by myself during the years 1869, 1870, and 1871, with the exquisite views of Dawes in 1857 (Monthly Notices of R. A. S.,' xviii. 8, 50, 72), presents so much similarity in various respects, as to lead to a curious suspicion that the whole atmospheric shell of the planet, without any material disturbance in its relative arrangements, may have been shifted Southward by more than half the breadth of the equatorial zone; the South torrid belt, identified by its attendant festoons, occupying at that time a position very near the centre of the disc; while several of the characteristic features of what we have termed the South temperate zone and belt are to be recognised in a corresponding position of greater remoteness from the Pole. So lively was the first impression of this that I thought it might have been at once accounted for by a reversed presentation of the planet's axis; but on considering the dates, as well as the position of a satellite sketched by Dawes in transit, I found that no such explanation could be admitted. However little weight may be due to such a comparison, it suggests, at any rate, the desirableness of micrometric measurements of the latitude of the principal belts during future oppositions.

THE INTERNATIONAL EXHIBITION AT SOUTH

KENSINGTON.

BY S. J. MACKIE, C.E.

[PLATE LXXV.]

HE present Exhibition is by no means comparable with the magnificent affairs of 1851 and 1862 in this country, and in France in 1855 and 1867. The professed purpose of the annual Exhibitions at South Kensington, now understood to be inaugurated, is the illustration of the special progress made in particular sections of manufactures and science in respective decades of years. In the present-the first of the series-woollen materials, machinery, and fabrics, are supposed to be specially represented. Pottery is also an item. These two groups of manufactures and industries are expected to be on their trial, and the advance made since 1862 to be recorded in the reports which are to be published. Pictures, sculptures, and the various illustrations of the fine arts, as well as inventions, will always find admission, and, like the flowers in the Horticultural Gardens which the Exhibition buildings inclose, will blossom in full vigour year by year. The second and following Exhibitions will be devoted specially to other branches; until, after a decade of Exhibitions, the return will be made to woollen and pottery, and then will recommence another series of similar competitions.

The Horticultural Gardens form nearly a square area, containing about twenty-two acres; and the present permanent Exhibition buildings have been erected along the east and west sides, in blocks of two storeys each. At one end of the gardens portions of the exhibits are located in corridors leading to the Albert Hall, in which also a great number of pictures, fabrics, educational and other articles, are arranged. Across the opposite end of the Gardens there are temporary buildings, where the Meyrick collection of armour, military weapons," astronomical and other instruments, are displayed. The two