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64 we have already seen, no shadows are visible. If the canal could contain water, we should say that at this point it overflowed its banks, for the darkening now spreads out in all directions down both the inner and outer slopes of the crater wall. Whatever really occurs, it would be interesting to see what would happen to this dark area if the canal could by any means be cut off from it for a few weeks.

In Figure 3, to the left of the prominent canal and nearly parallel to it, a lighter one is found whose course follows in part the position of certain cracks seen in Figure 1. This same canal is well seen in Figure 5, but its companion to the eastward has shrunken and apparently moved away from it down the slope of the outer crater wall. This shrinking and shifting of position is confirmed by other drawings made during both July and August. The same thing has been observed on Mars, but owing to the difficulty of the observation the shifting has generally been ascribed to defective drawings. The two canals are found to be equally dark 6.5 days after lunar sunrise, or about the time of full moon. Before that date the western canal is found to be much the fainter of the two, after that date the eastern one. In Figure 8 the eastern canal has either entirely disappeared or its place is occupied by a long, narrow line. A new dark marking, due, perhaps, largely to shadow, has appeared just to the west of the western canal, which now for several miles follows pretty closely inside the crest of the crater rim.

It seems to the writer that the importance of these observations lies primarily in the aid they may give us in the interpretation of the real significance of the markings on Mars, but incidentally, also, in exemplifying the tenacity with which life will exist throughout the universe in situations that seem to us, from our ignorance, most unfavourable and most unsuited to it. A study of these markings should assist us in the study of those upon Mars for the following reasons: In the first place, as previously noted, the lunar canals are more readily seen than those upon Mars; the observer must not, however, expect to find them easy objects; it can merely be said that, with good seeing, they are not very difficult. In the second place, they are visible to advantage everywhere upon the Earth throughout the year, hence many more observations of them can be obtained by the same observer. Thirdly, they go through more rapid changes, and the same conditions are frequently repeated, so that a failure to observe a particular phase on one evening is readily remedied by another observation made a few months later. Fourthly, a greater number of individual specimens occur, scattered mainly in the lower latitudes, giving opportunity for a greater variety of conditions, and therefore a better chance