140 CARNEGIE INSTITUTION OF WASHINGTON. 



constituents must either be of deep-seated origin or their original atmospheric 

 relation has been changed by selective solubility in the magma. Deville's 

 laws respecting the variation in the composition of volcanic gases with the 

 distance from an eruptive center or with passing time are not supported by 

 the great body of evidence. 



There is evidence to show that a more or less abrupt evolution of gas from 

 the magma occurs during crystallization, but it needs further support. 



Chemical energy from shifting equilibria may have a considerable influence 

 in prolonging the life of an eruption, but not in initiating or rejuvenating 

 volcanic activity. Surface combustion in particular instances is probably an 

 important factor in keeping up temperature. Secondary volcanic explosions 

 of great violence are undoubtedly produced by the access of surface water to 

 hot volcanic ejecta. Some primary explosions are probably of the same 

 character; others, according to the best evidence, are the result of pressure 

 from magmatic gases, not the result of chemical action. 



(441) The crystal structures of the cuprous haUdes. Ralph W. G. Wyckoff and Eugen 



Posnjak. J. Am. Chem. Soc, 44, 30-36. 1922. 



This determination of crystal structure outlines the manner of application 

 of the general method of study, based upon the theory of space-groups, to 

 cubic compounds of the type RX (where R and X are atoms of the same 

 valence) when all of the diffraction data are furnished by a study of the powder 

 photograph from the crystal. 



Cuprous chloride, cuprous bromide, and cuprous iodide all have the zinc- 

 sulphide arrangement of their atoms in crystals. The lengths of the sides 

 of the unit cubes in the three cases are 5.49, 5.82, and 6.10 a. u. 



(442) Two corrections to mineral data. N. L. Bowen. Am. Mineralogist, 7, 64-66. 



1922. 



The material from Vesuvius, which has been described as a mineral species 

 and named rivaite by Zambonini, is found to be a piece of ordinary cobalt 

 glass that has been partially devitrified by the heat from the volcanic material 

 with which it is associated. It now consists of prisms of wollastonite em- 

 bedded in glass and can not be regarded as a mineral species. The so-called 

 reaumurite from Mont Pelee is probably identical. 



The optic axial angle (2V) of monticellite from Magnet Cove is given in all 

 textbooks as 37° 31'. This is really the value of V as originally determined 

 by Penfield and Forbes. With this knowledge that the optic axial angle of 

 monticellite is large, it is possible to identify as monticellite the unknown 

 "mineral A" of Larsen and Foshag. 



(443) The chemistry of the Pacific volcanoes : The limitations of our knowledge. Henry S. 



Washington. Proc. Pan-Pacific Scientific Conference, 1920 (Spec. Pub. 

 Bishop Museum, No. 7), pp. 325-345. 1921. 



The paper gives a r^sum4 of our knowledge of the chemistry of the volcanic 

 rocks of the Pacific Basin. The volcanoes are referred to two main groups: 

 (1) The Circum-Pacific volcanoes are continental and encircle the ocean from 

 the southern end of South America, through Alaska and Japan, as far as 

 New Zealand. Their lavas are very constant in chemical composition, 

 average high in silica, and are not markedly alkalic. (2) The Intro-Pacific 

 volcanoes are those which occur on the islands scattered through the ocean. 

 They are dominantly basaltic in character, but there are many decidedly 

 alkalic types. It is shown that our knowledge of the whole region generally 

 is very meager; thus we have only about 60 analyses to represent the long 

 line of gigantic Andean volcanoes and only about 130 to represent the very 



