Sei'TEM1!er 13, 1894] 



NA TURE 



477 



At the commencement of the observations (May 31) 

 the planet was 98,000,000 miles away, and his south 

 pole was directed towards the earth at about 23^', 

 reaching a maximum dip of 2^ on June 22, the 

 disc appearing gibbous to the extent of about one-sixth. 



Such being the conditions of seeing, one could look on 

 the planet, so to speak, rotating under one, watching 

 the snowy pole whirling, as a boy might look at his colour- 

 striped top. The observations were thus limited more or 

 less to the southern hemisphere, but occasional glimpses 

 carried one up as far as latitude 40 north The regions 

 most referred to in the observations were the Syrtis 

 Major, all the region of the north pole, that about Solis 

 Lacus, Lacus Phctnicis, and that a little more north of 

 Mare Sirenum and Mare Cimmerium. 



The rapid diminishing of the huge snow-cap, which at 

 this period of the planet's summer has been taking place 

 very rapidly, has perhaps been the most prominent 

 feature of this series of observations. Mr. Lowell has 

 noticed a decrease in its diameter of about ~' '" *s few as 

 fifteen or sixteen days, by no means a small diminution 

 considering the length of the period. 



A further very prominent feature of this polar cap is 

 the apparently perfectly elliptical outer edg,-., which 

 means that the boundary is in reality circular. The 

 narrow dark streak girdling it, and of nearly a uniform 

 breadth, is "clearly w^ater at the edge of the melting 

 snow, a polar sea in short. ' 



On the snow-cap itself, in the region of the great bay 

 situated south, Hellas and Chersonesus, several ex- 

 tremely brilliant parts have been observed, the appear- 

 ance and behaviour of which have led to the conclusion 

 that we are here dealing with mountains. These at 

 present are accounted for by supposing that the rotation 

 of the planet brings ihem into such positions that the 

 sun's light can be reflected by them in the direction 

 of the earth, just as a beam of sunlight can be thrown by 

 means of an ordinary mirror. What has led us to believe 

 them to be mountains is the constancy of the positions 

 in which they are, for not only have they been several 

 times observed at this period of opposition, but Mitchell 

 in 184;, in a drawing made at Cincinnati on August 30, 

 and Green in 1877, have both recorded them and in 

 the same position. 



Another marking on this polar cap, referred to as "the 

 great rift," seems to be a very conspicuous object. The 

 best time for observing it is when it is, so to speak, end 

 on, or on the central meridian of the planetary disc. Mr. 

 Lowell has likened it to " a huge cart-track coming down 

 to one over the snow," and he has estimated its size as 

 220 miles broad and 1200 miles in length. 



An observation, which is of more importance than one 

 is at first likely to admit, is that concerning the /wr/ty^w/Ve- 

 characters of all the markings between the sharp boundary 

 of the snow-cap and the definite characters of the con- 

 tinental coast-line. The coast-line was " most salient 

 and clear cut on the western side of the Hour-Glass Sea 

 (Syrtis Major or Mer du Sablier). To the eastward 

 the coast lay in general direction straight, approaching 

 the pole as it stretched eastward. It was indented by 

 numerous bays, but destitute of those comet-tail penin- 

 sulas so generally observed connecting it to the chain of 

 islands south. All of these islands, Hellas, Ausonia, and 

 the rest, were \ague, without definite contours, and lapsed 

 imperceptibly mto the surrounding seas. Even in colour 

 they were less decided than, though of much the same 

 tint, as the continental areas." 



With such facts before us, it is hard to believe that we 

 are not observers of a great inundation, which obliterates, 

 or nearly so for a time, all landmarks lying anywhere in 

 the region 20 or more south of the equator. The source 

 of this flood would of course be the rapidly melting 

 snow, and the great volume of water now liberated from 

 the solid form, and forming at the boundary of the cap 



NO. 1298, VOL. 50] 



the dark narrow belt, would be ample to account for the 

 disappearance of islands, blurring of coastlines, and such- 

 like phenomena. Certain are we that these landmarks 

 are there, and the only justifiable cause of their dimness 

 of outline and colour is the hypothesis of their partial 

 and sometimes total submersion. 



An observation of great interest may be mentioned 

 here, as it deals directly with the great variation of sur- 

 face markings we have referred to above. The most 

 conspicuous object on the planet's surface at the present 

 time is the large black gulf bounding the melting snow, 

 and situated due south of the Hour-Glass Sea, or Syrtis 

 Minor. This, as Mr. Lowell has previously described 

 it, is clearly water at the edge of the melting snow, or, in 

 other words, a polar sea. On June 4 the polanscope was 

 brought to bear on this gulf by Prof Pickering, with the 

 result that it was declared to be water, just as the canal 

 in the same region, running north from it, was concluded 

 to be of this substance. This observation simply veri- 

 fied what had previously been thought to be the case 

 from its general appearance and colour ; but another 

 examination, at a later date, represented the matter in 

 quite a different light. On July 9 "no trace of the 

 polarisation in the dark spot could be detected," and a 

 more minute examination of the colour of this region 

 showed it to be of a " rich chocolate-brown tint, differing 

 entirely in colour from the bluish-grey regions to the 

 north of it." This reads somewhat different from 

 Lowell's observation on July 9 : " Bay a deep blue, looks 

 just as deep water does." Prof Pickering is of opinion 

 that as the colour of the grey regions does not, he 

 thinks, represent water, he is led to conclude, as far as 

 his observations at present go, that the " permanent water 

 area on Mars, if it exists at all, is extremely limited in its 

 dimensions." This favours to a considerable extent the 

 hypothesis of an inundation. 



Let us consider for a moment the observations relating 

 to the appearance of the channels at this time. These, at 

 this season of the Martian southern hemisphere, are 

 generally not so easy of observation, but Mr. Lowell has 

 been able to make out several of them. Those most 

 generally seen were Cerberus to the north of Mare 

 Cimmerium (on June 9 glimpsed as double), Eumenides, 

 Gigas, Titan, Gorgon and Sirenius, all of which lie just to 

 the north of the Mare Sirenum, and at a later date he 

 has seen some in the region of the Lake of the Sun Solis 

 Lacus^, namely Phasis, Eumenides, and Agathodasmon. 

 These channels, including one or two others which we have 

 not mentioned in the above list, have, we may say, the 

 greatest southern latitude, or lie nearest to the south 

 pole, a fact which may or may not be insignificant. 



Of course the great inclination of the pole of Mars 

 towards us, renders those on the northern hemisphere 

 more difficult of observation, so that our information 

 is to a great extent restricted. Nevertheless, one is 

 inclined, from Mr. Lowell's drawings, to look upon the 

 channels simply as the watercourses caused by the inun- 

 dation of the sea on to the land, commencing naturally 

 at the lowest levels, and of course at the water's 

 edge. Out of the nine drawings which he gives, illus- 

 trating the positions of the canals observed, eight 

 of them show the m.ijority of the canals in connec- 

 tion with the southern seas, while there is only one 

 instance of a channel not so connected, and that a very 

 short one. This is as it should be if the channels are, so to 

 speak, overtlow courses, and accounts also for the invisi- 

 bility, or at any rate the difficulty of observation of the 

 channels, as a whole, about this time. .-Xs the polar cap 

 ceases to melt, the channels should then be at their 

 fullest, and therefore easily visible. The absence of 

 cloud on the planetary surface about this time shows 

 that the aqueous circulation is almost totally brought 

 about by this fiood season. 



Whatever may be the cause of these channels and 



