148 CARNEGIE INSTITUTION OP WASHINGTON. 



(462) The average chemical composition of igneous rocks. Frank W. Clarke and Henry S. 



Washington. Proc. Nat. Acad. Sci., 8, 108-115. 1922. 



This paper presents a series of about 50 averages of the chemical composition 

 of the igneous rocks of various countries and continents, together with a final 

 average of the average chemical composition of the igneous rocks of the earth, 

 expressed both in oxides and as elements. In the latter, estimates are made 

 of the order of abundance of many of the rare elements. These averages are 

 to appear with full discussion in a forthcoming Professional Paper of the 

 U. S. Geological Survey by the same authors, entitled "The composition of 

 the earth's crust." 



(463) The nephelite syenite and nephelite porphyry of Beemerville, New Jersey. M. 



Aurousseau and Henry S. Washington. J. Geol., 30, 571-586. 1922. 



The scattered contributions to the geology and petrology of the alkalic 

 igneous rocks of northern New Jersey are reviewed in chronological order and 

 a general account of these rocks is given. The large mass of nephelite syenite 

 northwest of Beemerville is described and is interpreted as a lenticular sill or 

 a flat laccolith of foyaite, intruded by a mass of nephelite porphyry (probably 

 a dike) and by a small dike of leucite tinguaite. 



New analyses of the nephelite syenite (foyaite) and of the nephelite por- 

 phyry are presented and the affinities of these rocks and of leucite tinguaite 

 are discussed. It is concluded that these three rocks are textural and min- 

 eralogical variants, without chemical differentiation, of the same magma. 



It is shown that the nephelite porphyry is not a sussexite, as formerly sup- 

 posed, and the status of sussexite as a rock variety is considered, with the 

 conclusion that the name should be retained in its original sense, but that 

 the nephelite porphyry of Beemerville can no longer be regarded as the type 

 of the variety. 



The presence of zirconium and the rare earths in the Beemerville rocks has 

 been established, and the wide distribution of these elements in the region 

 east of the Appalachians is briefly discussed. 



(464) The determination of the space-group of a cubic crystal. Ralph W. G. Wyckoff. 



Am. J. Sci., 4, 175-187. 1922. 



Criteria which are valid for crystals which have any atoms of appreciable 

 scattering power in general positions are established for determining from 

 studies of Laue photographs the space-group to which a cubic crystal should 

 be assigned. This knowledge is of value to the crystal anatyst because it is 

 thus possible to tell how the atoms in many chemically complicated crystals 

 are arranged, even though existing methods are not sufficient to locate these 

 atoms with accuracy, and because an assignment of a crystal to a particular 

 space-group defines completely the positions of all of its elements of sym- 

 metry. Many of the space-groups give diffraction effects which are different 

 from those given by any other groups, and hence a method is provided, in 

 the cases of crystals assignable to any of these unique space-groups, of defining 

 completely crystal symmetry without making use of the older methods, such 

 as face development and the like. 



(465) Possible causes of the volcanic activity at Lassen Peak. Arthur L. Day. J. 



Franklin Inst. 194, 569-582. 1922. 



An address delivered before the Commonwealth Club of San Francisco on 

 July 21, 1922. 



The address contains a brief account of the volcanic outbreak of Lassen 

 Peak which began in 1914 and continued for nearly 4 years. Practically all 

 of the phenomena observed during this period of activity were the direct or 



