October 21, 1892.] 



SCIENCE. 



235 



may have been its weakness in the past it is now doing valuable 

 work. It is well equipped, has an able Faculty, and a demand 

 upon it greater than it can now supply. We see no reason why 

 it should not be a very valuable auxiliary in the future develop- 

 ment of the mining resources of the State. 



LETTERS TO THE EDITOR. 



#** Correspondents are requested to be as brief as possible. The writer's name 

 is in all cases required as proof of good faith. 



On request in advance, one hundred copies of the number containing his 

 cortimunication will be furnished free to any correspondent. 



The editor will be glad to publish any queries consonant with the character 

 of the journal. 



On the Interpretation of the Markings on IVIars. 



In view of the large mass of conflicting observations of Mars 

 now being reported, it occurs to me to mention one principle of 

 interpretation which has not to my knowledge been suggested. 

 On Mars, as on the moon, may it not be true that the most con- 

 spicuous permanent markings are due, not to land and water sur- 

 faces, but to contrast of mountain and plain? Mars through even 

 a large telescope is brought scarcely closer than the moon appears 

 to the naked eye, and it presents a general marking analogous to 

 the " man in the moon," which we know to be but a shadow 

 feature. (See, for example, Plate xxxiii. in Astronomy and 

 Astro-Physics, October, 1893). If the permanent water surface of 

 Mars is only one-half the area of the Mediterranean Sea, as lately 

 estimated by Professor Pickering, It is, of course, impossible that 

 the light and dark patches represent land and water; but the sup- 

 position that they represent, in general, open plain and rugged 

 hill-country throws light on certain perplexing phenomena. The 

 so-called canals are then prcbably mountain ranges separated by 

 plateaus, and the so-called duplication is a bringing out by higher 

 powers of outlying spurs and ranges, which with lower powers 

 are either indistinguishable or mingled with the general mass. As 

 our seeing improves, we may expect triplication, quadruplication, 

 etc. An observer on Mars looking through a telescope at the 

 Rooky Mountains from a distance of 100,000 miles would discern 

 merely a long dark blur, while upon closer scrutiny he might 

 distinguish parallel and off-shoot ranges with their foot-hills as 

 separate dark lines, which might be termed " canals." The ap- 

 parent straightness and regularity of the "canals'" is doubtless 

 the effect of distance. 



By this interpretation we solve the difHculty suggested by Pro- 

 fessor Pickering in Astronomy and Astro-Physics, October, 1893, 

 p. 669, that some " very well developed canals cross the oceans." 

 These " canals," then, are billy peninsular extensions or ranges of 

 mountainous islands. From Mars, Italy or Java would appear 

 but as dark streaks in a greenish or bluish medium. Mr. Barnard 

 mentions in the same number (page 683) that " long luminous 

 streaks" seem to be a definite feature of the planet's surface. 

 These are probably lines of snow-capped peaks. We must, on the 

 whole, believe that the seas, lakes, and canals of Schiaparelli's 

 map are as mythical as the seas of the moon. 



When one compares the extremely diverse drawings of Mars 

 given in the October Astronomy and Astro-Physics, one cannot 

 but suspect that clouds have a large part in producing this diver- 

 sity. The general appearance of the earth from Mars would cer- 

 tainly change from hour to hour from this cause alone. Pre- 

 dominant and cloud fog probably caused the " absolutely colorless, 

 dark- gray " appearance of the Martian oceans, noted by Professor 

 Pickering for a considerable time {Astronomy and Astro-Physics, 

 p, 546 cf., p. 669). Similarly the North Atlantic, which might 

 often appear from Mars as a blue or green spot, might for some 

 time, in the spring of the year especially, be a dark-gray patch. 



We must consider it likely that some of the rapidly darkening 

 spots which Mr. Pickering observed were due rather to springmg 

 vegetation caused by showers on barren tracts than to inundation, 

 particularly the case he mentions where a dark area suddenly ap- 

 peared to the "south east of the northern sea and of fully double its 

 area." It seems hardly possible, if the snows on Mars are as light 

 as Professor Pickering represents, that such extensive inundatiofls 

 could occur; and it is simpler and more in accord with general 



analogy that many such temporary dark or gray-green spots should 

 be due to vegetation rather than to water. 



Professor Pickering did so admirably with his 13-inch instru- 

 ment, that we may well believe that, if he had had a 30 or 40- inch 

 telescope, he would now be able to give us a tolerably accurate 

 account of the general physiography of Mars. We hope his appeal 

 for a thorough equipment will meet a ready response. 



HraAM M. Stanley. 



Lake Forest University, Oct. 11. 



The Lines on Mars. 



In Science, Sept. 23, Mr. C. B. Warring communicates a theory 

 to account for the gemination of the so-called canals of Mars. 

 He suggests that the phenomenon may be due to a defect in the 

 eye of the observer by reason of its possessing the power of 

 double refraction in some or in all directions. That some eyes do 

 possess the power of double refraction is a well-known fact. It 

 is a defect which, I imagine, is much more common than is gen- 

 erally supposed. It may be suggested that data representing a 

 large number of oases might show astigmatic eyes to possess the 

 power of double refraction more frequently than others. I do 

 not know that any data have been collected upon this point. 



Concerning the existence of the canals of Marsand that they are 

 sometimes really double, I have no doubt. My own recent work 

 at the Lick Observatory has convinced me that they are not illu- 

 sions due to imperfect eyesight. During the present opposition, 

 I spent about thirty nights in the work on Mars, working with 

 Professors Schaeberle and Campbell. On about half the nights I 

 saw the so-called canals with more or less distinctness, but on 

 • only one occasion did I clearly see a canal double. This was 

 August 17, when the canal called Ganges on Schiaparelli's map 

 was clearly seen to be double, and was so drawn in my note-book. 

 That the doubling was real and not apparent is evident from the 

 fact that Professors Schaeberle and Campbell both saw the same 

 canal double on the same night, and drew it so. Other canals, 

 some of them nearly parallel to Ganges, were seen that night, but 

 none of them appeared double. 



Our work was done independently. In turn each went to the 

 telescope, and made a drawing of what he saw. We did not see 

 each others' drawings, nor did we talk of what we had seen. It 

 was not until the next morning that we learned that each had 

 seen Ganges double. Wilejam J. Husset. 



Leland StaQford, Jr., University, Palo AJto, Cal. 



A New Habitat of the Black-Throated Rock Swift, Micropus 

 Melano!eucus. 



As curator of the museum, I have just procured for the State 

 University of Nebraska a set of bird-skins prepared during the 

 past summer, among which are five skins that must be of interest 

 to ornithologists. They verify the discovery made by Professor 

 Lawrence Bruner of the University of Nebraska, that the White- 

 throated Rock Swift builds and breeds in the precipitous bluffs 

 around Squaw Canon, Sioux Co., Nebraska, and, what is more 

 likely, throughout the Pine Ridge regions, as Professor Bruner 

 has observed them also at Crow Butte, near Crawford, Nebraska. 



This isolated habitat of the White- throated Rock Swift, Micro- 

 pus Melanoleucus (Panyptila Saxatilis), is several hundred miles 

 east of its most eastern limits as known hitherto. Perhaps the 

 Pine Ridge Buttes and bluffs, particularly those about Squaw 

 Canon, are fo admirably adapted to their nesting and high-flying 

 habits as to be the attractive forces. 



Although five specimens were secured, no eggs were found. It 

 should be mentioned, perhaps, that the egg of this swift is un- 

 known. However, it is the expectation of the author that they 

 will be found on some of his own, or some of the other numerous 

 e-xcursions sent annually to this excellent field by the university. 



The nests are built high up in the cliffs, in the most inaccessible 

 places. The semi-lithified sandstone of these buttes is easily ex- 

 cavated; and, as nearly as could be learned, the swifts dig back 

 about eighteen inches, the opening barely admitting the hand 

 but expanding somewhat at the nest. The nests are built of 

 grass. 



