228 Some Recent American Petrological Literature. 



"Geological Observations in Fiji. Part II : Petrography of Fiji," 



by W. G. Foye. Proc. Amer. Acad. Arts and Sci., vol. liv, 



pp. 97-145, 1918. 



Petrographic descriptions are given of a large number of rocks 



collected by the writer in the islands of the Fiji group. They 



include tonalite, gabbro, porphyrite, pitchstone, andesite, basalt, and 



various pyroclastic types. Besides the phi tonic intrusions four 



periods of extrusion are recognized, grading from acid to basic, all 



types being subalkaline and probably differentiates of a basaltic 



magma. 



" The Nepheline Syenites of Haliburton County, Ontario," by "W. G. 

 Foye. Amer. Journ. Sci., vol. xl, pp. 413-36, 1915. 



A petrographic description of two differentiated laccoliths of 

 nepheline syenite, together with a discussion of the origin of such 

 rocks in general : it is supposed that the solutions that gave rise to 

 them were produced by the reaction of limestone with granitic magma. 



"Eruptive Rocks at Cuttingsville, Vermont," by J. W. Eggleston. 

 Amer. Journ. Sci., vol. xlv, pp. 377-410, 1918. 

 This small complex includes a large number of alkaline types 

 ranging from essexite to nordmarkite, with their accompanying 

 apophysal and complementary dykes. They are very similar to the 

 rocks of Mount Ascutney, Red Hill, and Essex County in New 

 England, and to the bosses of the Monteregian province, Quebec. 



"The Origin of Serpentine: a Historical and Comparative Study," 



by W. N". Benson. Amer. Journ. Sci., vol. xlvi, pp. 631-731, 



1918. 



Chrysotile and antigorite serpentines are alteration products of 



peridotites, more or less pyroxenic ; the hydration being often brought 



about by waters from the same magma. Sometimes it is due to 



water from later intrusions or to the general underground circulation. 



An extensive bibliography of serpentine is appended. 



" Magmatic Differentiation in Effusive Bocks," by S. Powers and 



A. C. Lane. Trans. Amer. Inst. Min. Eng., vol. liv, pp. 442-57, 



1917. 



An investigation of gravitative differentiation - phenomena in 



effusive rocks shows a concentration of leucocratic minerals near 



the top and of melanocratic minerals near the base of the flows, 



while chilled margins show the original composition. 



" Triassic Igneous Bocks in the vicinity of Gettysburg, Pennsylvania," 



by G. "W. Stose and J. Y. Lewis. Bull. Geol. Soc. Amer., 



vol. xxvii, pp. 623-44, 1916. 



Subsidence and faulting of Triassic sediments was followed by 



intrusion of prevalently diabasic magma, its products ranging from 



olivine diabase through hypersthene diabase to quartz diabase, or 



even nearly pure quartz-felspar micropegmatite rocks. 



