E. N. E. & W. S. W. and N. N. W. & S. S. E. inclined canals number 6 + 5 = 11 -- -- -- 33 18 51 a fairly equable division in direction. A trend to the westward would be given a particle descending from the north to the equator by the planet’s rotation, thus turning it southwesterly; and one to the west to a particle travelling equatorwards from the south, turning it northwesterly. As the doubles lie in the northern hemisphere, either in whole or part, to the extent of 93%, this might account for the preponderating tilt to the east of north and west of south exhibited by them. It would correspond with the lines of flow. To see whether this be so we will take only those double canals that lie exclusively in the northern and southern hemispheres respectively, and note those in the former that trend to the west of south as against those that run to the east of it, and _vice versa_ in the southern. In the northern the proportion of the westerly to the easterly ones is 17 to 4; in the southern, 1 to 0 the other way. Of those whose course is common to both hemispheres we find for the ratio of the southwesterly to the southeasterly 8 to 7. But the proportion of the course of these canals in the two hemispheres is on the side of this same ratio. From their direction we now pass to consideration of their distribution in longitude. It appears that some meridians are more favored than others. The hemisphere which has the Syrtis Major for centre is more prolific in them than its antipodes. From longitude 80° to 200° there are ten doubles, from 200° to 320° twenty-four, and from 320° to 80° seventeen; or, roughly, in the proportion of 2, 5, and 3. That this distribution means anything by itself is doubtful; it is much more likely to be a general topographical consequence of their distribution in another direction, which proves to be highly significant and which we shall now expose—that of latitude. If we separate the surface into zones, each ten degrees wide, and count the doubles found traversing in whole or part the several zones, we find the following arrangement:— Column Headings: A = At Opposition of 1903 Alone B = At All Oppositions so far observed at Flagstaff