176 PHYSICAL GEOLOGY. 



Yolcanic Outbursts which accompanied and followed the Formation 

 of the Alpine System. Geol. Mag. dec. ii. vol. iii. pp. 529-538. 

 At the climax, in Miocene times, of volcanic activity, a chain of 

 volcanos traversed the Atlantic from Tristan d'Acunha to Pranz Josef 

 Land, sending off two lateral chains, one on each side of the Alpine 

 area of depression — the northern through Germany, Austria, and S. 

 Russia; the southern through Spain, Italy, Asia Minor, and ^. India. 

 The enormous elevations accompanying these outbursts account for the 

 glacial beds associated with subtropical fauna. Arctic and E. European 

 fossils disprove periodical changes of climate. The " Glacial Epoch " 

 of W. Europe and E. America was purely local, like the more recent 

 glaciation of New Zealand. The existence in the past, as now, of con- 

 tinents proves that elevation neutralizes subsidence and denudation. 



W. H. D. 



Kittredge, G. P. A Consideration of Facts bearing upon the Question 

 of the Condition of the Earth's Interior. Pp.16. 8vo. Buffalo. 



Maintains the theory of central heat. From the evidence of wells, 

 mines, geysers or hot springs, and volcanoes it is proved that the tem- 

 perature of the earth steadily increases with depth. E,. B. N. 



Lory, — . Sur les Dislocations des Eoches dans les Pays de Mon- 

 tagues. [Dislocations in Mountain Districts.] Cornet. Rend. 

 Assoc. Fran(^. 1875, p. 679. (Abstract.) 

 Foldings produce schistose structure and distort fossils. Faults in 

 soft beds produce inversions. 



Mallet, R. On the Mechanism of Production of Volcanic Dykes, 

 and on those of Monte Somma. Quart. Journ. Geol, Soc. vol. xxxii. 

 pp. 472-495. 



The result of observations made on the direction of the dykes of 

 Monte Somma. Of 27 measured, the direction of but 5 or 6 passed 

 near the axis of the Yesuvian cone, the others all widely differed ; 10 

 were nearly vertical ; of the others, 38° was the maximum inclination 

 from the vertical. Intersections, &c. proved the dykes to be of different 

 ages. The axes of air-bubbles are nearly horizontal and parallel with 

 the plane of the dyke, from the dyke- substance having flowed horizon- 

 tally. A difference between the two surfaces of a dyke was in some 

 cases observed, and is not accounted for. The process by which the 

 dykes have formed is likened to the bursting of a cannon. There is a 

 normal pressure of the liquid lava in the crater which causes the fissures ; 

 but, from the thickness of the wall being great in proportion to the 

 cavity of the crater, the fissures seldom reach through. The material 

 of a cone being far from uniform, the fissure will be deflected to the 

 line of least resistance ; hence the deviation from a radial direction, 

 which makes the dykes an unsafe guide for determining crater-position. 

 The amount of injected dyke-material is not enough to alter palpably 

 the slope of the mountain. F. D. 



