Mr. Browning and Mr. Proctor, enables us to see this remarkable globe as though a photograph had been taken from a cloudless planet such as the moon.

But although there are many matters relating to the planet, that can only be the subject of our speculation, yet many of the moving processes of nature absolutely in action can be discerned by us. Thus the annual contraction and extension of the snowy zones at the poles, by alternative melting and freezing, can be distinctly perceived, and have been measured. This indeed constitutes one of the most interesting features connected with the planet, as bearing a strong analogy to the circumstances of our own globe. We know the poles of the earth are ice-bound: the appearance therefore of a white circular patch at the poles of Mars led Sir William Herschel naturally to the conclusion that the white revealed there was snow and ice, as on the earth; and closer scrutiny revealed the highest probability of this fact by the partial annual or seasonal disappearance, or contraction and expansion of the outline or boundary of the snowy region in the Martial summers and winters. The familiar phenomena of melting or thawing and freezing, as on the earth, were naturally and irresistibly suggested and exhibited; also snowing, and its consequent disappearance. Accordingly these regions were carefully measured at the corresponding seasons, and found to diminish or increase on a regular scale in proportion to the advance or retreat of the summer rays. Thus the magnitude of the South Pole was found to diminish gradually from June 16th, 1830, to July 19th of the same year, from a diameter of 12° 46′ to 8° 2′. The following is the table of observed changes :—

June 16th (the period answering to that month in Mars), the diameter of the snowy spot was

12 46

II 30

July 9th,
July 19th,

5 46

8 2

The rapid melting of the snow and ice will be here perceived, implying a reduction (in less than a month) of more than half the diameter; also the equally rapid increase on 10° from July 9th to the 19th. The border of the snow-zone on June 16th stretched to the latitude of 83° 37′; on the 9th of July only reached to 87° 7′ latitude. This was at the South Pole. The same result attended the observation of the North Polar spot,-the minimums of both taking place at the same time of the year, answering to the 12th of July, or the 12th of January on the earth.

The diminution of the extent of the polar snows was, however, found to be unequal, the Southern spot undergoing a much greater diminution both in extent and distance from the pole than the North, the latter having an area when at its maximum of five times that of the South; thus proving that while the South Pole has a hotter summer than the North, it has a colder winter,— a greater extent of snow and ice in winter, and a consequent greater variation of climate than the North, being subjected to greater extremes of heat and cold. The snowy extension of the Southern Pole reached in Feb. 7th and March 7th, 1837 (answering to Dec. 10th in Mars), the distance of 35° from the South Pole: in other words, to a latitude answering nearly to the British Islands on the earth. Thus there will be colder winters

in the southern regions of Mars than in the north, and hotter summers, and this notwithstanding the summer and spring in the northern parts are seventy-six days longer than in the south; but the greater heat and light received in the south compensates for its shorter summer, being 0.52 that of the earth at the south, and only 0.37 at the north. From these considerations Mædler arrived at the conclusion already put forward by the elder Herschel, "that in these white spots we behold a wintry effect, similar in every respect to a fall of snow upon the earth at that season."

But besides the general retreat of the snowy zones in summer, smaller changes and movements have been seen in these regions, some of which doubtless may be attributed to clouds of great extent moving, as ours do in similar cloudy regions on the earth; but others more probably arise from local causes, such as are experienced in our Arctic regions, such as the breaking up of ice packs and fields, and some of the changes observed even from a temporary fall of snow. Thus Professor Mitchell, of Cincinnati, relates in July, 1845, the sudden appearance of a strange dark spot in the very midst of the bright snow patch, and which was seen by several friends as well as himself. This spot having remained stationary for some time, disappeared, and was never seen again, being probably an extensive cloud. Again, on August the 29th of the same year, the entire outline and configuration of the snow zone was changed rapidly from the appearance and outline it had maintained for weeks: this was evidently the breaking up of a vast field of ice, a phenomenon familiar to all our Arctic explorers. Again, on the 30th of August, Professor

Mitchell saw a small bright spot, which was projected on the snowy zone, gradually detach itself from it, and moving onwards for a few days get out of the snowy regions altogether, after which it gradually became. fainter, and at length disappeared. Some have imagined they saw this spot on the margin of the planet, and if so it was suggested that it might have been the Martial moon; but it is more probable that it was some vast bright snowy cloud moving away to a warmer region, where it was dissipated, as it would be here, presenting indeed a perfectly analogous case of meteorology with the earth.* The difficulty of observation of the surface

Mr. Proctor gives a most interesting account of the visible rising of a cloud or mist from the surface of the ocean called "Dawes' ocean" in the map, and which was witnessed by two astronomers the same night, the first part of the phenomenon by Mr. Lockyer and the conclusion of it by Mr. Dawes, who has recorded it in his sketch. He thus describes it :- "On October 3rd, 1862, Mr. Lockyer was observing Mars late in the evening. He noticed a part of Dawes' ocean, where it borders on Herschel continent, was hidden from view. In place of the ordinary dark aspect of this region, a faint misty light, with ill-defined borders, was observable. As the evening progressed, he noticed that the outlines gradually became clearer; but when he gave up observation (at about half-past eleven), the white light still continued to veil the outline of a part of Dawes' ocean. Now Mr. Dawes observed Mars on the same night, at a quarter-past twelve. The drawing which he took at that hour shows that the process of clearing up noticed by Mr. Lockyer as being in progress in the earlier part of the night, had, by the time Mr. Dawes began work, entirely lifted off the veil which concealed the coast line. The remains of misty light seen by Lockyer are still to be detected in Mr. Dawes' drawing; but they have passed further south, and no longer hide the shores of Dawes' ocean.'

Mr. Proctor makes the following interesting comment upon the above, as pointing to, and confirmatory of, the probable nature of the phenomenon then witnessed:"From the observed position of the region in question, the Martial time of day there must have been somewhere about noon when Mr. Lockyer began his observations; and about one o'clock in the afternoon, according to our terrestrial mode of reckoning, when Mr. Dawes "Other Worlds than Ours." (Page 96.)

+ Proctor.

of Mars arises quite as much, it must be remembered, from his own atmosphere as from ours; and the meteorology of the planet, which the spectroscope has revealed to be precisely similar to our own, leaves no doubt what to attribute such changes to, as, without leaving the earth, a similar picture is presented here. A very fine night for observation on the earth, however, may be a very bad one for seeing Mars, and vice versa.

The climate of Mars, so far as the proportions and divisions of the seasons are concerned as influencing it, ought to be quite as fine as the earth, and probably as warm. The spring, summer, and autumn, in his northern regions, occupy 522 days in all: ie., spring, 1911; summer, 181; autumn, 1491; while his winter lasts only 147 days (not quite five months) out of the 669 days, or nearly two terrestrial years. This large proportion of the finest seasons should give as the result a finer climate than we have," ceteris paribus." Thus upon observation alone with the telescope astronomers formed the theory of the analogy of Mars' meteorology to that of the earth more than a century ago, and that the white spots were his polar snows.

Where snow is there must be water, and vapour, and condensation into clouds; the formation of air, and all the kindred phenomena we are acquainted with here,— thunder, lightning, rain, hail, and frost, and all the atmospheric and magnetic conditions that are inseparable from them.

Then the dark "blue-green spots" were oceans,

observed the planet. It is no uncommon thing to see our terrestrial skies clear up soon after mid-day; and if the veil which conceals the Martial features is really cloudy, this is precisely what happened out yonder forty millions of miles away from us on the day in question." (Page 100.)