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.