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.
IV
Topography thus introduced to our notice for its effect on the breadth of the doubles proves upon inspection to be of extended application to the whole subject. Examined for position these canals turn out to have something to say for themselves bearing on the question of their origin and office.
With regard to position, probably the first query to suggest itself to an investigator to ask is of the direction in which they run. Is there a preponderance manifest in them for one direction over another? Do they show an inclination to the vertical, to the horizontal, or to some tilt between? To answer this we may box the compass, and taking the four cardinal points with the twelve next most important points between for sectional division segregate the doubles according to their individual trend. As we have no means of determining in which sense any direction is to be taken,—if indeed it is not to be taken alternately in each,—we get eight compartments into one or the other of which all the doubles must fall. This they do in the following manner:—
| S. & N., Laestrygon, [†]Fretum Anian, Aethiops, Amenthes, Titan, [†]Dis, [†]Is | 7 |
| S. S. E. & N. N. W., [†]Gihon, Ganges, [‡]Tithonius, Euphrates, Adamas | 5 |
| S. E. & N. W., [†]Eunostos, Triton, Tartarus, Naarmalcha | 4 |
| E. S. E. & W. N. W., [†]Astaboras, Typhon, [†]Pierius | 3 |
| E. & W., [†]Nar, [†]Protonilus, [*]Propontis, [‡]Nectar, [†]Cocytus, [†]Chaos | 6 |
| E. N. E. & W. S. W. [†]Deuteronilus, [†]Callirrhoe, [†]Cerberus N., Cerberus S., [†]Sitacus, [†]Erebus | 6 |
| N. E. & S. W., [†]Djihoun, [*]Nilokeras I & II, [†]Avernus, [†]Nepenthes, Gigas, [†]Alander, Polyphemus, [†]Gelbes, [†]Marsias, [†]Pyramus, [†]Nilokeras I, Asopus | 12 |
| N. N. E. & S. S. W., Jamuna, Phison, [†]Hyblaeus, Cyclops, Lethes, [†]Thoth, [†]Vexillum, [†]Hiddekel | 8 |
| 51 |
[*] Wide canals.