8. Fall of chimneys, cracks in the walls of buildings.
9. Partial or total destruction of some buildings.
10. Great disasters, ruins, disturbance of strata, fissures in the earth's crust, rock-falls from mountains.
[40] In order to simplify these figures, the rivers, most of the inlets, and other details are omitted. Small figures are added along the railway lines to denote the distance in miles from the stations in Charleston.
[41] If this were so, the decrease in intensity would be only apparent; but it may have been real, and a possible explanation on this supposition is given later on (p. 135).
[42] If c be the depth of the focus, a the intensity at unit distance from the focus, and y the intensity on the surface at distance x from the epicentre, then
y = a / (c² + x²)
The inclination of the curve at any point is given by
dy / dx = -2ax / (c² + x²)²,
and this is a maximum when