196 REVIEWS 



proportion of the lateral to the vertical component of movement. As 

 already pointed out by several foreign critics, the report of the commission 

 is decidedly provincial in that it fails to take any account of work already 

 done upon earthquakes, and because all conclusions seem to have been 

 reached as though no other earthquake had been known or studied. Prob- 

 ably the most distinguished geologist of the commission has said of the 

 California quake: "That event was so far unforeseen that no seismologists 

 were at hand and the duty of investigation fell; in the emergency, on a 

 volunteer corps of geologists and astronomers" (Science, N. S., Vol. XXIX, 

 January 22, 1909, p. 122). While no doubt accounting for the notably 

 local aspect of the study, this hardly furnishes its excuse. The literature 

 of the subject is large and for the most part easily accessible. 



In his discussion in support of the theory advanced, Professor Reid 

 says, "there is a consideration which seems almost decisive in its favor." 

 This consideration is derived from trigonometric surveys made (I) 1851-65, 

 (II) 1874-92, and (III) 1906-7 (after the great quake). These surveys 

 show clearly that lateral displacements measured in feet occurred within 

 the wide zone bounding the great rift and in both the intervals I-II and 

 II-III. This result, it should be stated, is quite in harmony with modern 

 views of earth displacments. What is needed, however, in order to prove 

 Professor Reid's contention, is a determined lack of connection in time 

 between displacements during much shorter intervals and the earthquakes 

 which have been so frequent in the district. The crucial question to be 

 decided is whether a movement of a portion of the earth's outer shell was 

 true warping or was a displacement of individual parts per saltuni by repeated 

 small amounts. Reid's theory leaves the smaller and frequent temblors 

 altogether unaccounted for. 



The argument that the amplitudes of the displacements revealed in 

 the trigonometric data are greatest in the vicinity of the rift and fall away 

 rapidly from it, is without force, since we know that faults revealed in 

 geological sections quite generally show distribution of displacement 

 over a number of planes within a zone, and the trigonometric stations are 

 here so widely separated as to furnish no crucial data. There is, however, 

 one consideration quite out of harmony with the Reid theory. Rock 

 slabs which, by slow and continued application of stresses, have been forced 

 into warped surfaces have been found to take on a permanent "set" and 

 do not return by rebound to their original attitudes. As already pointed 

 out, the validity of the theory can be tested observationally through the 

 frequent "location" of monuments in earthquake countries and comparison 

 of the results with an accurate catalogue of local earthquakes. 



