Similarly, it is extremely probable that many portions of Tokio have from time to time been protected more or less from the severe shocks of earthquakes by the numerous moats and deep canals which intersect it. Although we are not prepared to say how far artificial openings of this description are effectual in warding off the shocks of earthquakes, from theoretical considerations, and from the fact that their use has been discovered by persons who, in all probability, were without the means of making theoretical deductions, the suggestions which they offer are worthy of attention. _General conclusions._—The following are a few of the more important results which may be drawn from the preceding chapter:— 1. In choosing a site for a house find out by the experience of others or experimental investigation the localities which are least disturbed. In some cases this will be upon the hills, in others in the valleys and on the plains. 2. A wide open plain is less likely to be disturbed than a position on a hill. 3. Avoid loose materials resting on harder strata. 4. If the shakings are definite in direction, place the blank walls parallel to such directions, and the walls with many openings in them at right angles to such directions. 5. Avoid the edges of scarps or bluffs, both above and below. 6. So arrange the openings in a wall, that for horizontal stresses the wall shall be of equal strength for all sections at right angles. 7. Place lintels over flat arches of brick or stone. 8. To withstand destructive shocks either rigidly follow one or other of the two systems of constructing an earthquake-proof building. The light building on loose foundations is the cheaper and probably the better. 9. Let all portions of a building have their natural periods of vibration nearly equal. 10. If it is a necessity that one portion of a building should have a very different period of vibration to the remainder, as for instance a brick chimney in a wooden house, it would seem advisable either to let these two portions be sufficiently free to have an independent motion, or else they must be bound together with great strength. 11. Avoid heavy topped roofs and chimneys. If the foundations were free the roof might be heavy. 12. In brick or stone work use good cement. 13. Let archways curve into their abutments. 14. Let roofs have a low pitch, and the tiles, especially those upon the ridges, be well secured. CHAPTER VIII. EFFECTS OF EARTHQUAKES ON LAND, 1. Cracks and fissures—Materials discharged from fissures—Explanation of fissure phenomena. 2. Disturbances in lakes, rivers, springs, wells, fumaroles, &c.—Explanation of these latter phenomena. 3. Permanent displacement of ground—On coast lines—Level tracts—Among mountains—Explanation of these movements.