Apkil 14, 1916] 



SCIENCE 



541 



Throughout the vast extent of the Pacific Ocean 

 scattered volcanic islands furnish us with material 

 evidence of the composition of the suboeeanic 

 portions of the lithosphere. A thorough investiga- 

 tion of the rocks of these islands will contribute 

 to our knowledge of the distribution of various 

 igneous rocks, that is, to the problem of petro- 

 graphical provinces which involves the question 

 of lateral heterogeneity of the earth. 



Closely allied to this is the problem of isostacy, 

 or the relation between the major features of the 

 relief on the earth's surface and the density of 

 the underlying lithosphere. Igneous rocks from 

 continental regions should average lighter than 

 those from deep oceanic regions. Preliminary 

 estimates appear to confirm this expectation, but 

 much more data regarding the rocks of deep sea 

 islands are needed to establish the relationship. 



An exhaustive study of the rocks of the Pacific 

 islands will determine the character of each group 

 as either the summits of volcanoes built up from 

 the sea bottom or partly submerged remnants of 

 a former continental area. 



Afternoon Session 



2.30-6.00 P.M. — Auditorium, National Museum. 

 A New Form of Metamorphism : Akthue Keith 



(introduced by Geokge F. Beckee). 



Many Appalachian rocks are known which ap- 

 pear to be massive plutonics and have been, called 

 quartz diorite. Some evidence against this was 

 known from the first, but their metamorphie nature 

 is now considered settled. These rocks form 

 bodies with shapes usually somewhat elliptical, 

 but also lenticular, in sheets or dike-like masses. 

 Their larger relations are: (1) gradation into the 

 enclosing rocks; (2) occurrence only in gray- 

 waeke or similar rocks; (3) thickness, rarely over 

 three feet; (4) lack of igneous rock in the same 

 region; (5) presence at many horizons; (6) oc- 

 currence over thousands of square miles. The 

 principal minerals are quartz, hornblende or bio- 

 tite, garnet, albite and oligoclase, the most con- 

 spicuous being hornblende, biotite and garnet. 

 These obliterate the older minerals, and their 

 prisms are disposed at random in marked con- 

 trast with the older parallel structures. The most 

 striking assemblage is a spheroid composed of 

 concentric shells of different mineral contents. 

 These rocks were metamorphosed from graywaeke 

 or similar rock under heat and pressure but no 

 movement. They raise anew the old question of 

 the formation of igneous rocks from sediments. It 

 appears, however, that they were not fused as a 



mass, but that their individual minerals grew 

 through the agency of solutions. The process is 

 of wide extent and is available as an accessory in 

 forming plutonic rooks. 



Contributions to the Petrology of Japan, Philip- 

 pine Islands and the Dutch Indies: J. P. Id- 

 dings and E. W. Morley. 



Volcanic rocks have been collected from thir- 

 teen active volcanoes and from other localities in 

 Japan, and chemical analyses have been made of 

 sixteen of them. The igneous rocks of Luzon, 

 P. I., were collected and studied, and six analyses 

 made. They bear strong resemblances to rocks of 

 Japan. In the Dutch Indies the leucitic rocks of 

 Java, Bawean and Celebes were collected, together 

 with the associated lavas and intrusive rocks. Of 

 these twenty-nine have been analyzed, besides 

 seven from Timor and Sumatra. The leucitic 

 rocks of Celebes were found to be much more 

 extensive than heretofore supposed. 



SYMPOSIUM ON THE EXPLORATION OF THE PACIFIC 



(Continued from the Morning Session) 

 The Extent of Knowledge of the Oceanography of 



the Pacific: G. W. Littlehales. 



The accumulated oceanographical observations 

 in the Pacific relate principally to the surface and 

 the bottom. The intermediate depths have been 

 little investigated. The materials from centuries 

 of voyaging and from the expeditions for sound- 

 ing the ocean sent forth since the last quarter of 

 the nineteenth century, when deep-sea soundings 

 first began to be taken in the Pacific, have pro- 

 vided- information of the distribution of baro- 

 metric pressure and winds over this vast tract and 

 also of the general aspects of surface circulation, 

 temperature and salinity. The manuscript sheets 

 of the United States Bathymetrical Chart, con- 

 taining all the authentic deep-sea soundings, are 

 offered in evidence to show the extent to which 

 the basin has been sounded and the distribution of 

 bottom deposits made known, and to prove the 

 inadequacy of existing measurements to define 

 the contours of configuration beyond the conti- 

 nental shoulder. In the North Pacific there is a 

 tract twice as large as the United States which 

 has been crossed by only a single line of sound- 

 ings at intervals about 250 miles wide apart; and 

 a number of instances exist in which tracts as 

 large as the United States remain entirely un- 

 fathomed. The deposits on the floor of the ocean 

 have generally been penetrated only to the depth 

 of a few inches, and little is known of their thick- 

 ness or stratification. Of the variations, from 



