174 



POPULAR SCIENCE NEWS. 



[December, 1888. 



The disk is mottled with spots and streaks, which 

 are not arranged in belts with an evident relation 

 to the planet's equator, as in the case of Jupiter 

 and Saturn, but are distributed irregularly over 

 the surface. A telescope of not more than seven 

 or eight inches aperture shows them fairly well, 

 and the more conspicuous of them can be seen 

 with much smaller instruments. As we watch 

 them, they drift across the disk from east to west, 

 and many of them are so permanent and well 

 defined, that by their help we can ascertain the 

 length of the planet's day with very grfeat accuracy. 

 The latest and probably most precise determination 

 is that of Bakhuyzen, who gives the time of rota- 

 tion as 2ih. 37m. 22.66s. The only question is as 

 to the odd hundredths of a second. 



Most of the spots and markings are permanent, 

 but not all. Bright patches are now and then 

 observed which seem to be evanescent, like sheets 

 of cloud that for a time conceal the oceans and 

 continents beneath, and then rapidly clear away. 



Such phenomena, of course, imply an atmos- 

 phere more or less' like our own, and Dr. Huggins 

 has confirmed the fact by a direct observation of 

 the lines of water-vapor in the planet's spectrum. 

 But many things go to show that this atmosphere 

 is much less dense and extensive than the Earth's. 

 On Mars great storms and widespread cloud-veils 

 are comparatively rare; for the most part the real 

 features of the planet's surface are clearly seen, 

 uncomplicated by overlying mists, while the sur- 

 face of the earth at any given moment would 

 probably be fully half obscured, as seen from the 

 Moon or Mars. 



The planet's equator is inclined to its orbit at an 

 angle of nearly 28°, and, as a consequence. Mars 

 ought to have seasons much like those of the earth. 

 One very beautiful phenomenon seems to show that 

 this is actually the case. In the neighborhood of 

 the planet's poles there are brilliant spots, evidently 

 composed of some substance which reflects light 

 very abundantly ; and it is natural to think of ice 

 or snow, because, as Sir W. Herschel observed a 

 century ago, each spot grows larger when it is 

 turned away from the Sun, and dwindles in the 

 summer, just as a polar ice-cap would. It is worth 

 noting that this snow-cap, if such it really is, never 

 comes down to middle latitudes, as does the wintry 

 envelope of our terrestrial snow. In January "the 

 man in the Moon " would see pretty much all that 

 portion of the Earth's northern hemisphere which 

 lies above 45° of latitude as one gleaming white 

 expanse, unbroken except where the Atlantic and 

 Pacific Oceans interrupt its continuity. Although 

 Mars is so much farther from the Sun than the 

 Earth is, and receives less than half as much heat 

 to each square mile of surface, it presents no such 

 prevalence of ice in either hemisphere. 



This can hardly be due to the scanty supply of 

 water, because the study of the planet's surface- 

 markings seems to indicate that nearly half the 

 globe is covered by seas and oceans ; not, indeed, 

 nearly so large a fraction of the whole as in the 

 case of the earth, but quite enough to furnish a 

 fair supply of rain and snow. 



The northern hemisphere of Mars is of a com- 

 paratively uniform orange-colored tint, and is sup- 

 posed to be mainly land, though it encloses certain 

 dark spots, which, likely enough, are inland seas. 

 The southern hemisphere, on the other hand, is for 

 the most part darker, with here and there islands 

 of the lighter- colored surface. From this south- 

 ern ocean, as it is supposed to be, great bays like 

 that of Bengal, and arms like the Red Sea and 

 the Baltic, penetrate deeply into the northern con- 

 tinent; indeed, as Proctor long ago remarked, a very 

 striking characteristic of Mars is the manner in 

 which land and w/iter are divided and intermeshed, 



there being on the planet no unbroken mass of land 

 to correspond to the Asiatic continent, nor any 

 ocean like the Pacific. 



The principal features of the planet's geography 

 (strictly areography) are now quite beyond ques- 

 tion, and have been several times fairly mapped. 

 Thus far, however, no satisfactory nomenclature 

 has been settled. Upon Mr. Proctor's map the 

 names assigned are mostly those of astronomers 

 who have made contributions to our knowledge of 

 the planet's topography. Thus we have the conti- 

 nents of Herschel, Dawes, Msedler, and Secchi, the 

 oceans of Dawes and De la Rue, and the seas of 

 Kaiser, Beer, and Delambre. Schiaparelli, on the 

 other hand, with better taste derives his names 

 from ancient geography and legend. We have for 

 the land masses, in the order before-mentioned, 

 Libya, Acria, Arabia, and Chryse. Syrtis Major 

 replaces the Kaiser Sea (which is, on the whole, 

 the most conspicuous object on the planet), and 

 De la Rue Ocean becomes the Mare Erythrseum. 

 But while the principal features of the planet's con- 

 figuration are thus fairly well made out, especially 

 those near its equator, there is no such agreement 

 in minor details, and the different maps are widely 

 at variance. Schiaparelli of Milan, who has had 

 the great advantage of the Italian atmosphere, has 

 introduced into his charts a great number of deli- 

 cate objects which have, never been satisfactorily 

 seen by others, though many partial confirmations 

 have been obtained. In place of the comparatively 

 ill-defined and hazy streaks seen here and there by 

 other observers, he represents the northern hemi- 

 sphere of the planet as covered by a network of 

 fine, hair-like lines, which he calls "canals," and 

 supposes to be water-ways. Some of these extend 

 over 90° of the planet's circumference, or nearly 

 3,000 miles in length, with a width not to exceed 

 30 or 40 miles. 



In Schiaparelli's map of 1877, which is the one 

 usually copied in the text-books, only a few of the 

 canals appear, but on his more recent charts there 

 are nearly sixty of them. 



The most remarkable thing about them remains 

 to be stated: In 1881 he found most of them to be 

 doubled ; the single lines which intersect the con- 

 tinental masses had almost without exception be- 

 come pairs of parallels, like the two tracks of a 

 railroad, with a very uniform distance of 150 or 

 200 miles between them. We say " had become," 

 because it is his opinion that this " gemination " of 

 the canals is a temporary phenomenon, depending 

 somehow on the progress of the martial seasons. 



These observations have naturally excited much 

 discussion, and at present scientific opinion is con- 

 siderably divided in legard to them. No other 

 astronomer has been able to observe the canals in 

 any such extent and perfection as Schiaparelli 

 with his telescope of only eight inches aperture; 

 but several others, especially Perrotin at Nice, 

 have seen something of the sort, and furnish a par- 

 tial confirmation of his work. The " gemination " 

 of the canals is so remarkable and so inexplicable, 

 that many are disposed to think the phenomenon 

 a purely optical one, due to some astigmatism and 

 imperfect focus of either the instrument or of the 

 observer's eye; or else (as Mr. Proctor suggested 

 rather vaguely) an effect of diffraction in some 

 way. 11 it were not for the observations of Per- 

 rotin, I for one should accept the theory of astig- 

 matism, for I have myself often seen delicate single 

 lines in the solar spectrum appear double from 

 some slight pinch of one of the lenses in the spec- 

 troscope. But it is very difficult to see just how 

 two different observers, with two such different in- 

 struments as the twenty-nine-inch telescope at Nice 

 and the little eight-inch at Milan, could see the phe- 

 nomenon alike if it were merely optical. There is 



some mystery about the matter, and it is clear that 

 we must wait for further and more conclusive evi- 

 dence before building any considerable structure of 

 theory upon the reported facts. The only sug- 

 gestion so far made which seems worthy of mention 

 here is, that the "canals" may be water-courses 

 of some sort, at times flooded, and at other times 

 drained off, so as to become invisible. 



During the last opposition (in April) the planet's 

 nearest approach to the earth was about 56,000,000 

 miles, and it was so far south in the sky, that it 

 could not be very well observed in Europe or this 

 country. But both at Milan and Nice some of the 

 canals were seen, and seen as double for a time. 

 Perrotin also reported that a continental tract 

 which he had named Libya (a part of Proctor's 

 " Herschel Continent ") had mostly disappeared, as 

 if inundated. While this observation of his is par- 

 tially confirmed by some observers, it has been 

 positively disputed by others. With the Lick tele- 

 scope, Libya was seen last spring by Professor 

 Holden on several occasions; in fact, whenever it 

 was favorably placed for observation at the time 

 the telescope happened to be directed on the planet. 

 Nor was any thing seen at Mount Hamilton like 

 the "gemination" of any of the canals, though 

 in some instances a widish streak was observed, in 

 place of the sharp and narrow line delineated on 

 the map. 



The two little satellites (discovered by Professor 

 Hall at Washington in 1877) were, of course, seen 

 and easily observed. 



It is to be hoped, and expected, that the great 

 telescope on Mount Hamilton, with its advantages 

 of situation and its freedom from the atmospheric 

 embarrassments which so seriously interfere with 

 the work of our other large instruments, will in 

 1890 and 1892 be able to solve definitely the inter- 

 esting problems that our neighbor proposes for our 

 investigation. 



Princeton, Nov. 9, 1888. 



[Original in Thf Popular Science 2^ews.] 



THE HISTORY AND MYSTERY OF A DEW- 

 DROP. 

 A CHAPTER FOR YOUNG PEOPLE. 

 BY SAMUEL BRAZIER. 



In any of the fairy scenes of nature what can be 

 found more innocent, more beautiful and pure, 

 than a morning dew-drop glistening in the cup of a 

 flower? Sometimes from a distance of several 

 yards away it reveals its presence by the bright 

 ray of light it has just received from the sun, and 

 flashes out again. You approach the glistening 

 little object, and try to look into its tiny depths. 

 From one point of view it is dark, almost black ; 

 from another it is so bright that you cannot look 

 into it at all: its reflected ray is. as pure and intense 

 as that of the most brilliant diamond. Then, 

 looked at in a different direction, it is clear and 

 transparent, looking so cool and beautiful. There 

 it is, trying to be a perfect little globe, which it 

 would be if it were not for the pressure of its weight 

 on the petals of the flower. But see, while you 

 look into it, and admire it, it gradually becomes 

 less and less, till, kissed by the rays of the morn- 

 ing sun, it vanishes away. The heat contained in 

 the rays of light that were passing through it was 

 sufficient to overcome the mutual attraction of the 

 molecules of water of which it was composed, and 

 alter its form from liquid to vapor. It has again 

 become invisible moisture, and floated away in the 

 air, from which, during the night, when the air was 

 cooler, and therefore more contracted, and unable 

 to hold so much moisture, the little dew-drop was 

 squeezed out into the cool cup of the flower. 

 Where did it come from, and how did it get into 



