PHYSICAL GEOLOGY. • 179 



Silvestri, Prof. The Eruption of Etna on the 29th August, 1874. 



Phil. Mag. ser. 4, vol. xlix. pp. 126-134. See also iV^. Jahrh. Heft i. 



pp. 36-42. 

 Translated from a pamphlet published in Catania. The account in 

 Italian is noticed in the Geological Eecord for 1874, p. 169. 



Thomson, Sir W. Underground Temperature. Coll. Guard, vol. 



xxix. J). 311. 

 Abstract of Address at the Annual Meeting of the Geol. Soc, Glasgow. 



Ward, J. C. Modem Yulcanicity. Geol. Mag. dec. ii. vol. ii. pp. 

 38-41. 



Criticises the theory of Mr. Mallet, who regards the volcanic forces 

 and movements of upheaval and depression of early geological periods as 

 more intense than those of recent date, and holds that the early vol- 

 canic phenomena were not 'explosive.' The author believes, from a 

 study of the volcanic rocks of Wales and the Lake District, that these 

 views are incorrect ; he shows that the upheaval of the Cumberland 

 mountains occupied an immense time — the length of the Old Eed 

 Sandstone period — represented by the denudation of 26,000 feet of beds. 



W. T. 



Ward, Dr. Ogier. On Slickensides or Rock-striations, particularly 

 those of the Chalk. Quart. Journ. Geol. Soc.wol. xxxi. pp. 113, 114. 

 Believes all slickensides to have been caused by motion. 



Williamson, Prof. W. C. Earthquakes and Volcanoes. Science 

 Lectures for the People. 6th ser. pp. 220-236. 8vo. Manchester, 



Willis, Jolin. Internal Heat of the Earth. Nature, vol. xiii. p. 8. 

 Discusses Prof. Mohr's observations on the internal heat of the earth 

 (see p. 177). 



Woodward, C. J. On an Apparatus to illustrate the Ponnation of 

 Volcanic Cones. Phil. Mag. ser. 4, vol. 1. pp. 52-3. 



A simple apparatus of a trough, with a bladed screw to carry forward 

 material, and a bellows to eject it through a hole in a board laid above, 

 will produce cones, illustrating many volcanic phenomena in a way 

 suited to the lecture-room. P. D. 



See also : — 



Clark, D. R. Underground Temperature, St. Gothard Tunnel : p. 199. 



Doelter, Dr. C. Volcanic Group of the Ponza Islands : p. 59. 



Hunt, Dr. T. S. Chemical and Geological Essays: post, under 

 Miscellaneous and General. 



Suess, Prof. E. Origin of the Alps : p. 101. 



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