172 PHT8ICAL GEOLOGY. 



Eruption d. Aetna am 29. Aug. 1874. [Thoughts and Studies on 

 Vulcanism, with special relation to the Earthquake of Belluno on 

 June 29, 1873, and the Eruption of Etna on Aug. 29, 1874.] 

 Pp. xxiv, 320 ; 13 plates. 8vo. Oratz. 



Fisher, Rev. 0. Mr, Mallet's Theory of Volcanic Energy tested. 

 Phil. Mag. ser. 4, vol. 1. pp. 302-319. 



Objects to Mr. Mallet's paper that the cube of rock supposed to 

 be crushed under great pressure cannot be extended laterally, and 

 therefore Mr. Mallet's experiments do not prove what heat would 

 be evolved. With respect to the " combined influence of friction and 

 rock-crusTaing," maintains that though this quantitatively may be 

 enough to account for the volcanic energy, qualitatively it is not ; that 

 is, it cannot be localized so as to produce the effects. Calculations 

 are given to show that the amount of heat thus evolved on that 

 part of the plane of shearing or friction where the heat is greatest is in 

 small proportion to all the work done. Explains that instead of pro- 

 ducing volcanic energy the work of descent of the crust is transformed 

 into : — 1, heat within the nucleus ; 2, work of relative elevation of 

 the crust ; 3, heat within the crust. As an alternative explanation of 

 volcanic phenomena, surmises that the earth's volume has diminished 

 by the escape of steam, which in a superheated state conveys heat 

 from below, and keeps lava melted. E. D. 



Eemarks upon Mr. Mallet's Theory of Volcanic Energy. 



Quart. Journ. Oeol. Soc. vol. xxxi. pp. 469-478. 

 Takes up in succession the sections of Mr. Mallet's paper read before 

 the Hoy. Soc, agreeing with many and discussing some. Objects to 

 the conclusion that the oceanic and continental areas have occupied 

 nearly the same positions from the first — the marine origin of most 

 strata, and the need of terrestrial conditions elsewhere for furnishing 

 the detritus, pointing to an opposite conclusion. With regard to the 

 main question*, of the cause of volcanic heat, Mr. Eisher cannot see 

 why the heat developed by rock-crushing should be localized, and 

 therefore cannot allow the lateral pressure caused by the shrinking of 

 the earth's crust to have been sufficient to fuse the rocks. E. D. 



Uniformity" and " Vulcanicity." Geol. Mag. dec. 2, vol. ii. 



pp. 97-99. 



Objects to the doctrine of uniformity as understood by some authors, 

 which is that the forces of nature act upon matter which has always 

 been in the same condition as at present. Mr. Mallet's theory requires 

 to be considered from his own point of view, and with the aid of 

 mathematics. His critics have hardly touched the essence of the 

 question. W. T. 



Forbes, W. A. A Visit to Vesuvius. Bej^. Winchester Coll. Nat. 



Hist. Soc. pp. 84-89. 

 A general account of the mountain. 



