III
Turning from such generic characteristics to more specific traits, the first thing to strike an attentive observer is that the doubles differ in width; that they are not mensurably alike in the property they hold in common of being paired. In some the twin lines are obviously farther apart than in others, and the relation persists however repeated the observations. Of two doubles the one will always surpass its fellow. This contrasted individuality first struck me in the Phison and the Euphrates; and from the first moment at which these doubles showed as such. The Phison pair seemed perceptibly the narrower of the two. A like distinction was evident at the next opposition and the next; in fact, at every succeeding one to the present day. Nor was the recognition of the fact confined to me. If we turn to Schiaparelli’s Memoriae we shall find that that master had registered the same idiomatic width for the two canals from first to last throughout his long series of records. The observation thus made proved to apply to each and all of these curious twins.
Diversity in width for different doubles appears plainly in drawings where more than one double is depicted. As an example, two drawings are here given in the text, made, the one on July 13, 1905, λ15°, and the other on July 20, λ313°. In them the Phison, Euphrates, Djihoun, and Thoth appear contrasted as unmistakably as either of them does with the single canals apparent at the same time. That this drawing is typical is borne out by all the best measures of the several doubles as seen at successive oppositions, and marshaled in the subjoined list. How truly individual the quality is stands proved by the relative values in different years which are even more accordant than the absolute ones.
The canals were:—
| Width | ||||
| 1903 | 1905 | Mean | ||
| 1. | Phison | 3.5 | 3.4 | 3.4 |
| 2. | Euphrates | 4.0 | 4.2 | 4.1 |
| 3. | [*]Protonilus | 2.8 | 2.0 | 2.4 |
| 4. | Deuteronilus | 2.2 | 2.4 | 2.3 |
| 5. | Pierius | 2.5 | — | 2.5 |
| 6. | Callirrhoe | 2.5 | [*]2.1 | 2.3 |
| 7. | [*]Hiddekel | 3.8 | 4.9 | 4.3 |
| 8. | [*]Gihon | 3.9 | 4.9 | 4.4 |
| 9. | Djihoun | 2.0 | 1.9 | 1.9 |
| 10. | Sitacus | 3.8 | [*]3.3 | 3.6 |
| 11. | Jamuna | 4.5 | — | 4.5 |
| 12. | Ganges | 5.0 | 5.2 | 5.1 |
| 13. | Nilokeras I and II | 11.0 | 11.7 | 11.3 |
| 14. | Nilokeras I | 2.3 | — | 2.3 |
| 15. | Gigas | 3.5 | — | 3.5 |
| 16. | Laestrygon | 2.2 | — | 2.2 |
| 17. | Cerberus N. | 4.0 | — | 4.0 |
| 18. | Cerberus S. | 4.0 | — | 4.0 |
| 19. | Cyclops | 2.9 | [*]2.2 | 2.6 |
| 20. | Nar | 2.6 | 2.0 | 2.3 |
| 21. | Fretum Anian | 2.8 | — | 2.8 |
| 22. | Aethiops | 3.3 | — | 3.3 |
| 23. | Eunostos | 2.8 | — | 2.8 |
| 24. | Lethes | 2.9 | — | 2.9 |
| 25. | Marsias | 3.2 | — | 3.2 |
| 26. | Hyblaeus | 3.0 | — | 3.0 |
| 27. | Amenthes | 3.2 | 3.5 | 3.3 |
| 28. | Thoth | 2.8 | 2.3 | 2.5 |
| 29. | Nepenthes | 2.8 | 2.3 | 2.5 |
| 30. | Triton | 2.7 | [*]2.3 | 2.5 |
| 31. | Pyramus | 2.9 | [*]2.0 | 2.5 |
| 32. | Astaboras S. | 3.2 | 3.1 | 3.1 |
| 33. | Tithonius | 2.6 | 2.2 | 2.4 |
| 34. | Vexillum | 3.5 | 2.9 | 3.2 |
| 35. | Tartarus | — | 2.7 | 2.7 |
[*] Poor.
Here we have widths ranging from eleven degrees to two. The widths given are those when the canal was at or sufficiently near its full strength, and are measured from the centres of the constituents. We notice two points: the agreement of the same canal with itself and its systematic disagreement with others. But what is especially to the point, if we compare the values found at successive oppositions, we find that for different canals the values agree in their difference. This shows that each of these values is, in most cases if not in all, a norm for that particular canal; a value distinctive of it and to which it either absolutely or relatively conforms. In other words, the width of the gemination is a personal peculiarity of the particular canal, as much an idiosyncrasy of it as its position on the planet.
Two general classes may be distinguished; those up to about five degrees in width apart and those above this figure. Whether such very widely separated lines as go to make up the second class, such as the Nilokeras I and II, constitutes a double is a debatable point. Schiaparelli thought they did, and so classed them. To me it did not at first occur so to consider them, and in some instances, such as the Helicon I and II, later observations seem to justify the omission. With the Nilokeras I and II the outcome seems the other way. The reasons for distrust of a physical relation between the constituents is not so much the distance separating them, nor any lack of parallelism, as the self-sufficient manner in which they show alone. Even this, however, tends to be recognized in the narrower pairs as they come to be better seen. It may be that width alone is wholly competent to selective showing. For the farther apart two lines are on the planet, the more opportunity is afforded the air waves to disclose the one without the other, a relative revelation which is constantly happening to detail in different parts of the disk. As long as any doubt exists of a physical community of interest, it seems best to distinguish such possibly merely parallel canals by suffixed numerals.
Of this class of doubles is the Nilokeras I and II. So wide is it that Mr. Lampland succeeded in photographing it as such, the two constituents showing well separated, and if it prove a true double it will be the first Martian double to leave its impress on a sensitive plate. Although separated by four hundred miles of territory, the two lines are parallel so far as observation can detect, which, of course, is not so very easy with the lines so far apart. In the country between one crosswise canal certainly lies, the Phryxus, and much shading thus far unaccounted for. Recent discoveries, however, point to the cause of such shading as lines imperfectly seen. For in some cases the lines have actually disclosed themselves, and warrant us in believing that it is only imperfect seeing that keeps the others hid. Of the pair the Nilokeras I is itself double, curiously reproducing what sometimes is seen in the case of double stars, one of whose components turns out to be itself a binary. The second line of the Nilokeras I lies close to its primary on the north, and was on the only occasion of its detection the merest of gossamers, while the Nilokeras I itself stood out strong and dark. Thus do these Martian details increase and multiply in intricacy the better the seeing brings them out.
In the case of the other doubles, the doubles proper so to speak, there is every indication of a physical bond between the pair. What that bond may be is another matter and seems to be of different divulging, according to the particular instance. At one end of the subject, both as the widest of these doubles and one of the most important, stands the Ganges. The components of the canal are 5°.1 apart. This great width, joined to the fact of scant extension, gives the canal a stocky aspect, its breadth being but one sixth of its length. Its width draws attention to it while the phenomena it exhibits intrigue curiosity.
As early as the first opposition of my observations in 1894, the canal, as it underwent the process of doubling, showed phases of peculiarity. It was first caught by me as a double over toward the terminator, or fading edge of the disk; then as it was brought nearer the centre by the gaining upon the longitudes, showed as a broad swath of shading of a width apparently equal to any it later exhibited. In this appearance it continued for some months, and then in October began to show a clarification toward the centre. Once started, the lightening of its midway advanced till at last, on November 13, it stood out an unmistakable double, the two lines standing where the edges of the swath had previously been. Had the observations here been all that one could wish, the method of gemination would have been certain and of great interest. Unfortunately, the observations left much to be desired, and those repeated in 1896-1897 and 1901 were of like doubtfulness. A period of swarthy confusion preceded the plainly dual state, but whether the double simply clarified or widened as well it was not possible to assure one’s self. That the canal exhibited plainly the effects of seasonal development was as unmistakable as the steps themselves were open to ambiguity. In 1903 the canal was at its minimum and hardly to be made out. It seemed then to show an actual change in width coincident with alteration of visibility. But this, too, could not be predicated with certainty. It was also surmisable that the westernmost line was the one from which the development proceeded.
In 1905 much more was made out about it, training in the subject and increased proximity of the planet contributing to the result. It now became clear to me that the canal did develop from the western side; for the western edge made a dark line of definite boundary from which shading proceeded to the eastern side, where it faded almost imperceptibly off with no defined line to mark its limit. That this shading gradually darkened was evident, but that when it could be seen at all it extended to the extreme limit of the eventual double, restricted the character if not the fact of an actual widening. At this opposition, too, the canal passed through its period of minimum visibility and was then seen, whenever it could be caught, as a confused swath of full width. In the case of this canal, then, a widening in the sense of a bodily separation of two lines seems inadmissible. On the other hand, the gradual darkening of the swath, and especially the advance of the darkening from the western side, points to an interesting process there taking place.
Peculiar development of the Ganges.
At the opposite end of the series stands the Djihoun. As the Ganges is the widest of the instantly impressive doubles, so the Djihoun is the narrowest the eye has so far been able to make out. Only two fifths of the width of the Ganges pair, this slender double is very nearly at the limit of resolvability. So well proportioned are its lines to the space between them, however, that in ease of recognition it surpasses many wider pairs. In form, too, it is distinctive, turning by a graceful curve the trend of the Margaritifer Sinus into the Lucus Ismenius. With its fundamental branch—the northern of the two—it joins what is evidently the main line of the Protonilus—also the northern one—to the Margaritifer Sinus’s tip.
Djihoun, the narrowest double.
It differs from the Ganges in some other important particulars besides width. In its case no band of shading distinguishes it at any time. It has always been two lines whenever it has been seen other than as a single penciling; the only confusion about it being evidently our own atmosphere’s affair. These two lines, furthermore, have showed, within the errors of observation, always the same distance apart. So that not only no change of intercommunication between the lines but no change in their places apparently occurs.
Between these extremes in width, two hundred miles more or less for the Ganges and seventy-five miles for the Djihoun, the distance parting the pairs of most of the double canals lies. From 3° to 3°.2 on the planet may be taken as that of the average; the degrees denoting latitudinal ones on the surface of Mars, the length of which is equal to thirty-seven of our English statute miles.
Most of the canals conform apparently to the type of the Djihoun rather than to that of the Ganges. Careful consideration of them fails to find any increase or decrease of distance, between the pairs of the same canal at different times, which cannot be referred to errors inevitable to observation of such minute detail. In short, the double is made by the addition of a second line in a particular position and not by a growth out to it of a line coincident to begin with with the first.
I have said that the average width between the two lines of the doubles was about 3°. It must not be supposed that this average width denotes anything more than an average; or, in other words, that it denotes anything in the nature of a norm. The remark is important in view of a suggestion which I have heard made that we have here a system based on fundamental Martian units, in which, or in multiples of which, the dimensions of the canals are implicitly expressed. Such, however, does not seem to be the case. In some instances, indeed, we have certain evidence to the contrary and that the width of the double is conditioned solely by antecedent place. The Phison and Euphrates offer a case in point. These two important arteries in duplicate leave, as we saw, from two carets in the Mare Icarium, the Portus Sigaei, held in common tenancy by both. Each pair then proceeds down the disk inclined at its own particular angle to the meridian in order to reach by a great circle course a certain spot; the Pseboas Lucus in one case, the Luci Ismenii in the other. As one of these angles is thirty-five degrees while the other is only three, they must, from the circumstances of their setting out, have not only different widths, but widths determinately different in advance, since each is, roughly speaking, foreshortened by the degree of divergence from the meridian. The one, therefore, must be about four degrees to the other’s something less than three and a half. This is what they actually are as determined by measurement from observation. That the calculated value agrees with that found from observation helps certify to a community of starting-points, but it completely does away with comprehensive design in the question of their widths. For if the one were so settled, the other could not be.
Indeed, the next example seems to deny it to both. This example occurs, too, not far away from the scene of the first, in the twin bays of the Sabaeus Sinus, from which depart, mutatis mutandis, the double Hiddekel and the two Gihon. These twin gulfs bear so little imprint of being other than natural formations, that they have been universally and very likely quite rightly taken for such ever since Dawes discovered them in 1859, long before things like canals were dreamed of. It is strange that when the Hiddekel and the Gihon were found by me to be double in 1897, with a branch of both leading from each bay, the connection between the sceptically scouted doubles and the thoroughly believed-in bays should have been apparent. For to link a ghost to materiality, if it does not discredit the materiality, serves to substantialize the ghost. Furthermore, it shows that in this case neither the one double nor the other can have had its width engineered on any preconceived scale, unless the twin bays be themselves so accounted for. So that it seems useless to seek for cryptic standards in the canals or to think to find them a measure of value from the fact of their being a medium of exchange.
The Sabaeus Sinus, embouchure for the double Hiddekel and Gihon.
A third instance of the same thing in the case of the Ganges and the Jamuna was proved at the last opposition after having long been suspected without my being able to make sure of it. These instances, taken in connection with the wide range of values in the widths presented by different canals, serve to show that the distance between the twin lines is an individual characteristic of the particular canal, and further to point to its cause, in some cases certainly and possibly in all, as topographical. The duplicate line makes a convenience of a neighbor, and suits its distance from its fellow to friendly feasibility. To cut a ‘canal’ to conform to the country seems logical if not obligatory, and quite in keeping with the nomenclature of the subject; but here the starting-point appears to be the only thing considered—the canal once safely launched being left to shift, or rather not shift, for itself.