310 Scientific Intelligence. 



" 1. Appreciable surface dislocations appear to be formed only 

 at the time of macroseisms, and the throws upon these plains 

 stand in some relation to the magnitude of the disturbance." 



" 2. The evident dislocations produced are, generally of two 

 orders of magnitude, those of the higher order being very limited 

 in number, while those of the lower order are often quite 

 numerous." 



" 3. Earthquake dislocations are normal faults with hades 

 approaching the vertical." 



" 4. A considerable lateral shift along the larger planes of dis- 

 location has sometimes been observed, and is probable in other 

 instances." 



" 5. The crustal movements indicated at the surface at the 

 time of earthquakes appear to be due to an adjustment in position 

 of individual blocks." 



So closely connected are fractures and seismic phenomena that 

 the fracture system suggests earthquake activity, while, on the 

 other hand, seismic methods may be used for locating fracture 

 systems. Hobbs has called attention to a number of regions 

 where this intimate correlation is brought out by observed facts. 

 In the chapter on Seismic Geography of the Eastern United 

 States and Canada, attention is called to the correspondence 

 between a map of the lineaments of the Atlantic Border Region 

 (Bull. Geol. Soc. Am., vol. xv, pi. 45, 1904), showing the promi- 

 nent fault lines, and a map of the Distribution of Earthquakes in 

 the United States (F. de Montessus de Ballore, Les Etats-Unis 

 sismiques ; Archives des Sci. phys. et nat. de Geneve, vol. v, 

 pi. 3, 1898), where a complete concordance is shown. This illustra- 

 tion is particularly striking because of the fact that the two maps 

 were made entirely independently and with different purposes in 

 view. Another important conclusion is suggested by the study 

 of the relation of earthquakes to fault lines, viz., that the local 

 value of gravity seems to be altered as the result of local dis- 

 placements which produced earthquakes. The far-reaching im- 

 portance of this conclusion as an aid in the explanation of 

 uplifted blocks, trough lines, and ocean valleys, is evident. The 

 law of distribution of seismicity, as stated by Montessus, Milne, 

 and others, considers earthquakes as directly related to regions of 

 marked change of relief, and is restated by Professor Hobbs in a 

 single sentence, viz., " Seismicity is localized on earth lineaments 

 — faults — and is greatest at their intersection." 



The Geotectordc and Geodynamic Aspects of Calabria and 

 Northeastern Sicily; by William Herbert Hobbs, with an 

 Introduction by the Count de Montessus de Ballore. Pp. 

 293-362, with 10 pis., 3 figs. Leipzig, 190V (Wilhelm Engel- 

 mann). — As stated by the author, this article is a study in orienta- 

 tion ; it is a geological study of a well-known earthquake 

 region, as compared with the usual investigation along physical 

 and commercial lines. The attitude of the author gives a clue to 

 the value of this work. After some twenty years' experience in 



