The curves of all the canals in a given zone have been combined into a mean curve or cartouche for that zone; and then the cartouches for the several zones have been represented and ranged according to latitude on the accompanying plate. Consideration of these mean canal cartouches is very instructive. In the first place not one of them is a straight line, either horizontal or inclined. All are curves and, with the exception of the top one, all show a minimum or lowest point during the period under observation. From this point they rise with the time, or to the right on the plate. A black star marks this minimum, and is found farther and farther to the right as one goes down the plate; that is, as one travels from the neighborhood of the arctic regions down to the equator and then over into the planet’s southern hemisphere. Drawing now a line approximately through the stars and remembering that the minimum means the date at which the canal started to develop, we see that the canal development began at the border of the north polar cap and thence continued down the disk over the planet’s surface, as far as observation permitted the surface to be seen, which was some thirty-five degrees into the other hemisphere. This is the first broad fact disclosed by the cartouches. [Illustration: _MEAN CANAL CARTOUCHES_ P.L.] Furthermore, the development took place at an approximately uniform rate. This is shown by the fact that the line passing through the black stars is approximately straight; for such straightness means that progression down the disk as measured by the latitude bore throughout the same ratio to the time elapsed.