various kinds of cracks and fissures. On the edge of a sloping sidewalk one may see the cracks due to a sliding, or lateral displacement of the surface; the effects of subsidence show a number of cracks around the area of depression; the growth of a tree crowding the asphalt shows the effect of lateral thrust, and an enlargement of a root below, or the effects of frost show cracks due to elevation. All these various cracks reveal the same features: they are discontinuous, they begin and end without definition. Schiaparelli says in regard to the _canali_ of Mars: "None of them have yet been seen cut off in the middle of the continent, remaining without beginning or without end." These lines on the surface of Mars, as a writer in "Nature" says, are almost without exception geodetically straight, supernaturally so, and this in spite of their leading in every possible direction. It is inconceivable that cracks should be laid out with such geodetic precision. We have seen that cracks have no definite beginning or termination; we have seen that the lines of Mars begin and end at definite places. Cracks are irregular, vary in width and differ entirely from the straight lines depicted by Schiaparelli, Lowell, and others. But if we admit them to be natural cracks in the crust we are compelled to admit that the forces implicated in such cracks must have been active many millions of years ago, as Mars, being a much older planet than the Earth, must have long since ceased to show those activities which the Earth, even to-day, exhibits in such phenomena as earthquakes, subsidences, elevations, and the like. Now cracks made at that early time in the history of the planet must have long since become filled with detritus and obliterated in other ways, and no evidence would show, even on close inspection, of their former existence, much less at a distance of 50,000,000 of miles, more or less. [Illustration: PLATE V 1. POTTERY CRACKLE 2 INCHES 2. MUD CRACKS 2 FEET 3. ASPHALT CRACKS 16 INCHES 4. EARTH CRACKS 10 FEET 5. CRATER CRACKS, MOON 55 MILES 6. _a._ MOON _b._ AFRICA 100 MILES 1500 MILES NATURAL LINES CRACKS, FISSURES, ETC.]