Geology and Natural History. 81 



beds have all the characteristics of lava flows, and raises the very 

 pertinent question why, if, as is claimed, the melaphyre and trap 

 dikes of the region are petrographieally hardly distinguishable 

 rocks, we find a huge dike of melaphyre amygdaloidal and scoria- 

 ceous in texture, while a three-foot dike of trap is a dense, holo- 

 crystalline rock. Attention is also called to the significant pres- 

 ence of well defined beds of tuff, a fact entirely overlooked by 

 Mr. Burr. In the light of these and other facts brought out by 

 Prof. Crosby it would seem, even to the casual reader, that the 

 weight of evidence is overwhelmingly in favor of a contemporane- 

 ous origin and that Mr. Burr's paper is thus the unintentional 

 cause of strengthening an exactly opposite conclusion from the 

 one given in the paper itself. 



In view of the fact that Prof. Crosby had, some twenty years 

 ago, fully described the " new interpretation " of the structural 

 relations of the Chestnut Hill slates to the northern conglomerate, 

 now presented by Mr. Burr, the word " new" seems, to say the 

 leasVrather superfluous. c. h. w. 



6. Sul Peviodo di forte Attivita esplosiva offerto nei rnesi 

 Aprile-3Taggio 1900 dal Vesuvio ; par R. V. Matteucci. Boll 

 della Soc, Sisin. Ital., Vol. vi, 8°, 110 pp., 6 pi., 1901.— This volume 

 gives a detailed account of the phenomena and products attend- 

 ing the period of explosive activity of Vesuvius at the time men- 

 tioned. The author begins with a general description of the 

 phenomena of the explosions, discusses their frequency and de- 

 scribes their effects on the crater, etc. He then discusses the 

 material ejected, the powder and sands, the lapilli, scoria, bombs 

 and solid blocks, each of which is made the object of particular 

 study. An immense quantity of these blocks were ejected, a 

 photograph being given of one containing twelve cubic meters of 

 material. Chemical determinations show that the ejected matter 

 was somewhat lower in silica than previous effusions of the vol- 

 cano. Some calculations of the force involved in projecting the 

 large block mentioned above are also given, showing that it 

 reached an altitude of about 300 meters. The work closes with 

 a discussion of volcanic explosions, both former ones of Vesuvius 

 and of other volcanoes as well. 



The plates are very beautiful and interesting heliotype repro- 

 ductions of instantaneous photographs, showing the form and 

 development of the smoke cloud from the great vapor puffs in 

 different stages and the swarm of projected blocks in mid-air. 

 The work as a whole is an excellent contribution to the study of 

 volcanic outbreaks in general and to the history of Vesuvius in 

 particular. l. y. p. 



7. Der Vulcan Etinde in Kamerun und seine Gesteine ; von 

 E. Esch. Sitzber. d. k. preuss. Akad. d. Wiss. zu Berlin, phys. 

 mat. Classe 1901, xn and xvm, pp. 41, figs. 22. — Etinde is one of 

 the smaller volcanos of the Cameroon Mts., a volcanic group cov- 

 ering some 150 square kilometers, close on the coast of western 

 Central Africa, and whose highest peak attains an altitude of 



Aii. Jour. Sci. — Fourth Series, Vol XII, No. 67. — July, 1901. 

 6 



