820 Revieics — The San Francisco Earthquake. 



mere length is not, however, its most remarkable feature. Throughout 

 its whole extent there was a sudden displacement of the crust, the 

 ground on the south-west side to a great but unknown depth being 

 shifted to the north-west, and that on the north-east side to the south- 

 east. The amount of the horizontal displacement varies considerably. 

 As a rule it lies between 8 and 15 feet, and in no place exceeds 21 

 feet. All structures which crossed the line of the fault were severed. 

 Roads and paths were displaced, sometimes by as much as their own 

 width or more, fences were snapped across and their ends separated, 

 piers were broken and shifted, and water-mains ruptured and telescoped. 

 These and other effects are fully illustrated by numerous photographs. 

 In other earthquakes there have been more pronounced changes 

 of elevation along the fault, but in no other known case have the 

 horizontal movements been so persistent over so vast an area. In 

 none, certainly, have the fault-movements been so carefully studied or 

 the investigations of the geologist been aided so effectively by the 

 researches of the biologist and the measurements of the surveyor. 



Among the minor sections of the report one of the most useful is 

 that which deals with the relations between the nature of the ground 

 and the intensity of the shock. The distribution of the damage in 

 San Francisco affords decisive evidence on this point. Though the 

 area covered by the city lies only a few miles from the fault, the 

 intensity of the shock was governed more by the nature of the under- 

 lying rock or soil than by proximity to the fault. In houses built on 

 rocky ground, especially on the summits of hills, many chimneys 

 remained unshattered ; on thick deposits of sand or earth, brick w^alls 

 were badly ci'acked and chimneys were generally destroyed; on 'made' 

 land, and most of all on that which occupies the sites of recently filled 

 creeks and marshes, ordinary buildings collapsed and even the best 

 masonry was seriously injured. The lesson conveyed could not be 

 more clearly enforced ; yet it is one to which the rebuilders of San 

 Prancisco are not paying all the attention which it claims. 



The only omission of any consequence in the book is the absence of 

 comparisons drawn between the phenomena of this and other great 

 earthquakes. If the San Francisco earthquake were the only shock 

 known to mankind, the attention paid to it could hardly have been 

 more exclusive. The examination of the points in which the 

 Californian fault resembles, or differs from, those of other earthquakes 

 might with advantage have been more detailed. The scantily observed 

 sound is described, but no surprise is expressed at its general in- 

 audibility. The valuable discussion on the distribution of damage in 

 San Francisco would have received ampler illustration if it had been 

 pointed out that similar relations between the amount of damage and 

 the nature of the ground have been noticed in many other earthquakes. 

 But comparisons such as these would have increased the size of volumes 

 already large enough and have delayed their publication. They can 

 be suggested by other writers, and there can be little doubt that in 

 this report there are facts described and photographs reproduced that 

 will form a veritable mine for workers in nearly every branch of 

 seismology. C. Davisok. 



