732 



SCIENCE 



[N. S. Vol. XXVII. No. 697 



rocks, and a part of the generalizations 

 based upon these were presented. A clas- 

 sification of the analyses according to the 

 types of igneous rocks brought out the fact 

 that, while the rocks of each group may 

 vary considerably among themselves, the 

 group as a whole fits into a logical place in 

 relation to the other groups. Arranged in 

 the order of the total volumes of gas 

 evolved per unit volume of rock, the types 

 of rock rank thus: (1) Basic schists, (2) 

 diabases and basalts, (3) gabbros and 

 diorites, (4) granites and gneisses, (5) 

 andesites, (6) syenites, (7) rhyolites. 



A classification on the basis of the age of 

 the rocks showed a rapid and steady de- 

 cline in the quantity of every gas in pass- 

 ing up the columns from Archean to Re- 

 cent lavas. Fine-grained rocks were found 

 to give off more gas than those of coarser 

 granularity. 



A series of special experiments showed 

 that the gases obtained from heating rock 

 material in vacuo come from three sources : 

 (1) Gas held mechanically in minute cavi- 

 ties and pores, (2) gas occluded within the 

 substance of the rock, and (3) gas produced 

 by chemical interaction between the non- 

 gaseous constituents of the rocks at the 

 high temperatures used. 



An average of 51 analyses of the gas 

 from igneous rocks, expressed in volumes 

 of each gas per unit volume of rock, gives 

 the following figures: H^S, .01; CO^, 2.16; 

 CO, .IB,; CH„ .05; H„ 1.36; N^, .09; and 

 total, 3.S5. 



It was found that rock powders which 

 had ceased to give off gas in combustion 

 tube, and were apparently exhausted of 

 their gas content, were able, when re-heated 

 after an interval of several months, to pro- 

 duce a considerable quantity of additional 

 gas amounting, in some cases, to as much 

 as half the volume originally obtained. 

 Test experiments showed that this was not 

 the result of a selective absorption of gases 



from the atmosphere during the interval, 

 but was due to some kind of diffusion or 

 molecular rearrangement going on slowly 

 within the rock material. 



The significance of these gases, existing 

 in a threefold state so generally and in so 

 large a variety of rocks, and their bear- 

 ings on some of the problems of vulcanism 

 and of the atmosphere were indicated. 



In the discussion that followed the read- 

 ing of this paper reference was made to the 

 bearing of the results upon the explanation 

 of causes of gas explosions in mines. Dr. 

 A. J. Holmes, chief of the technical branch 

 of the U. S. Geological Survey, in the 

 course of his remarks on the subject, gave 

 a report of progress of the investigations 

 undertaken by the survey to establish the 

 cause of the recent disastrous explosions in 

 coal mines. 



Work of the United States Reclamation 

 Service: E. T. Perkins, Chicago, Illinois. 

 This paper was a summary of the results 

 obtained by irrigation in the United States 

 and other countries, and a statement of the 

 work being done by the U. S. Reclamation 

 Service. 



Fjords of Puget Sound and the Saguenay: 

 Wabren Upham, St. Paul, Minn. 

 This paper presented the results of the 

 study of the Puget Sound and the Sag- 

 uenay regions. 



Puget Sound and its many long and nar- 

 row arms, called canals, from 100 to 600 

 feet in depth beneath the sea level, are ad- 

 mirable examples of fjords opening north- 

 ward, running thus toward the interior of 

 the ice-sheet which during the glacial 

 period covered this district, being the 

 southern part of the continental ice-sheet 

 west of the Rocky Mountains. It is impos- 

 sible to ascribe the depth of these fjords to 

 glacial erosion because they run in courses 

 opposed to the courses of glacial erosion 

 and transportation of material eroded. 



