386 REVIEWS 



fundamental theories of seismology. Seismological Science is for all these 

 reasons a work to which the future student will often be compelled to 

 refer. 



The centrum or volcanic theory of earthquakes which has so long held 

 the stage is here relegated to the lumber-room of the science, and for it 

 is substituted the conception that earth shocks are directly due to a mutual 

 adjustment of sections (** compartments") of the earth's crust which are 

 moved individually like blocks between the faults which bound them. 

 This new view-point is made the keynote of the entire work, and again 

 and again in the pages of Seismological Science it is pointed out how facts 

 before unintelligible or in direct conflict with others are now for the first 

 time explained and brought into harmony. To this view Professor Suess 

 has given his indorsement in the preface, where he has used the following 

 language: 



Seismic studies have passed by the same halting-places as the other branches 

 of our knowledge. And if, in order to reach some summit of our great moun- 

 tain chains, the Alpinist crouches upon a rock, not alone for the purpose of rest- 

 ing but that he may launch himself to greater heights after he has regained his 

 breath; so seismology started out from a simple and perfectly schematic con- 

 ception, that of the epicenter, the point of the earth's surface from which the 

 earthquake seemed to emanate, and all efforts were directed toward fixing the 

 position of this ideal geometric point; today seismology rejects this conception 

 as too much simplified and valuable only for the shocks due to volcanic explo- 

 sions, in order that it may rise to that of mutual adjustments within the design 

 of the terrestrial marquetry. 



De Montessus' classification of earthquakes is into macroseisms or 

 sensible earthquakes, microseisms or unfelt earthquakes registered by 

 instruments, and megaseisms or destructive earthquakes; and each of 

 these is treated in a separate part of the work. Considerable confusion 

 now exists as to the interpretation of the terms macroseisms and micro- 

 seisms, and the reviewer is of the opinion that Milne's usage, making macro- 

 seisms the more destructive earthquakes and microseisms the weaker 

 shocks, is better supported by derivation and practicability alike, though 

 the other view has perhaps the larger following. In the Count's usage a 

 microseism is a megaseism examined at a distance. The term microseism 

 as applied by de Montessus is also likely to be further confused with those 

 pulsational movements of pendulums which arise from causes other than 

 those which produce earthquakes. 



It is impossible in a brief review like the present to discuss the many 

 subjects which are treated in this most important monograph. It will be 



