488 



The effects produced, which are mainly available for such deter- 

 minations, he shows are divisible into four great classes : 1st. Fis- 

 sures or fractures produced in buildings, from whose direction, &c. 

 that of the wave-path at the point may be discovered : under this 

 head the author has minutely described and figured the forms and 

 peculiarities of fractures produced in all classes of buildings in the 

 region examined. The principles deduced being universally appli- 

 cable, he has shown the choice and precautions, &c. as to those best 

 fitted for seismic observation, and given formulae for the deduction 

 of the wave-paths, i. e. the direction in which the wave movement at 

 the point emerges. Velocity may also be determined from fissures ; 

 but this is more accurately ascertained from, 2nd, the overthrow 

 of bodies, such as columns, piers, walls, &c., either fractured at their 

 bases or simply overturned. 3rd. Fractures at the base without 

 sensible movement, or with oscillation within an observed arc short of 

 overthrow. 4th. The displacement of bodies by throw or projection, 

 such as vases, finials, balustrades, bells, coping-stones, tiling, &c. from 

 elevated points, in which, where the vertical height fallen, and the 

 horizontal range are observed, the velocity can be determined or the 

 direction of the wave-path and the angle of emergence of the wave ; 

 in certain cases all of these classes of displacement may occur 

 variously combined. All these resolve themselves into fracturing 

 forces, the movements of compound pendulums, and those of pro- 

 jectiles ; and in arranging the formulae for application, the author 

 acknowledges the important assistance rendered him by his friend the 

 Rev. S. Haughton, Professor of Geology in the University of Dublin. 



The author concludes the first part by a description of the cha- 

 racteristics of the towns and cities, buildings, &c. in the region 

 examined, of the physical features, the orographic and surface con- 

 figuration, and the geological structure of the south of Italy as em- 

 braced in his investigation. 



The second part embraces the application of these methods of 

 investigation, and the complete detail of the observations made by 

 the author in his journey from point to point, the working out at 

 many separate points of the directions of the wave-paths and angles 

 of emergence and wave-velocities, the explications of the numerous 

 and frequently singular and at first apparently perplexing circum- 

 stances, producing abrupt changes in the local intensity 'of seismic 



