Page:Great Neapolitan Earthquake of 1857.djvu/75

Rh of walls, buildings, or other objects affected by it. It will be convenient, therefore, to fix a nomenclature for these relations. A rectangular building, two of whose walls run north and south, and the other two east and west, may be called a cardinal building: buildings whose four walls run in any other azimuths will be described as ordinal.

Referring generally to the direction of wave transit in its horizontal component, or when nearly horizontal, as affecting cardinal buildings (which alone are generally suited for observation), it will be denominated normal when its azimuth is parallel to either pair of walls, viz., either north and south, or east and west.

When the line of wave transit, or its horizontal component, are in some intermediate azimuth, it will be said to be abnormal.

When a normal wave is an emergent one (the line of transit, or wave-path, inclined to the horizon) it will be called a subnormal wave; and in a similar case the abnormal wave will be designated as subabnormal.

These expressions will save much prolixity.

When the observer first enters upon one of those earthquake-shaken towns, he finds himself in the midst of utter confusion. The eye is bewildered by "a city become an heap." He wanders over masses of dislocated stone and mortar, with timbers half buried, prostrate, or standing stark up against the light, and is appalled by spectacles of desolation (such as those in Photogs. Nos. 15, 16, 17, 18, 19, and 20, Coll. Roy. Soc.).

At first sight, and even after cursory examination, all appears confusion. Houses seem to have been precipitated to the ground in every direction of azimuth. There seems