Reviews — Petrography of tlie Pacific Islands. 281 



I. — Petrographt of the Pacific Islands. Ey R. A. Daly. 

 Bull. Ueol. Soc. America, vol. xxvii, p. 325, 1916. 



IN this paper the author puts forward a proposal for a complete 

 scientihc exploration, geological, botanical, zoological, and 

 anthropological, of the islands composing the regions of Polynesia, 

 Melanesia, and Micronesia. These are scattered over an area 

 composing nearly one-sixth of the earth's surface, and the information 

 at our disposal concerning them is still very incomplete. The greater 

 part of the paper is taken up by a discussion of the petrography of 

 this vast region, so far as it is known. It is pointed out that what 

 may be called " continental " rocks, namely, plutonic, metamorphic, 

 and sedimentary types apart from coral-rock, are only found in islands 

 lying to the west of a line joining the easternmost of the Fiji group 

 to the Mariana Islands : all of these are fragments of an ancient 

 continent that broke up in Tertiary times. 



In several hundred other islands volcanic rocks have been recorded : 

 all the known occurrences are tabulated, and it appears that the 

 dominant types are olivine-basalt and pyroxene-andesite. Many 

 other varieties related to these, mostly of basic composition, have 

 also been recorded, and it is suggested that the andesites and the 

 iiltrabasic lavas are differentiates of a primary basaltic magma under- 

 lying the whole Pacific basin. The scarcity of acid lavas is 

 noteworthy: it suggests that in this region the ordinary crust of 

 quartzose sediments found in continental areas is absent. This is 

 in accordance witli the high density of the Pacific area as shown by 

 geodetic observations. From the evidence adduced it is clear that 

 this is a pre-eminently subalkaline province, and the author's 

 well-known theory of syntectic differentiation brought about by 

 absorption of limestone is applied to explain the genesis of a certain 

 number of occurrences of typically alkaline rocks, such as basanite, 

 nepheline -basalt, and varieties containing haiiyne. 



R. H.P. 



II. — The Mineral Industries of the United States. Sulpbur : 

 AN Example of Industrial Independence. By Joseph E. 

 PoGUE. Bulletin 102, pt. iii. United States National Museum 

 (Smithsonian Institution), pp. 10 and 3 plates. "Washington, 

 1917. 

 r I IHE falling off in the imports of sulphur from Sicily and of 

 i. pyrites from Spain consequent on the War has led to a great 

 development of the home supplies of sulphur in the United States, 

 and particularly of the native sulphur deposits of the Gulf Coast 

 region in Louisiana and Texas. Here the sulphur occurs in dome- 

 shaped masses in association with petroleum, rock-salt, and gypsum. 

 Many of the domes consist of a core of rock-salt with lenses of 

 gypsum and masses of limestone containing petroleum. In two 

 instances, at Sulphur, La., and Bryan Heights, Texas, bores showed 

 the presence of great masses of pure sulphur beneath several hundred 

 feet of quicksand. These masses are supposed to be essentially of 



