Januaey 17, 1902.] 



SCIENCE. 



with the dip of the strata (which is from 

 10 to 15 degrees) and the major group 

 with the strike. They are believed to be 

 formed along joints. The dip joint-veins 

 are normal to the plane of stratification, 

 the strike veins vary from normal to the 

 stratification, to verticality, and appear to 

 have been formed at different periods. The 

 grouping of the joint-veins in two direc- 

 tions appears in all the beds examined. 

 The scale of the jointing is related to that 

 of the bed, which is a thin one. 



Professor J. E. Wolf discussed the origin 

 of the jointing by contraction of the rock 

 on loss of water. 



Professor B. K. Emerson considered that 

 they had all the aspect of torsion joints as 

 produced in glass artificially. He referred 

 to Crosby's theory, according to which an 

 earthquake shock, passing through a stratum 

 in which a slight torsion was induced, would 

 produce the joints of the type described. 

 Gilbert considered Crosby's theory the 

 most plausible, and that the shrinkage 

 theory was not applicable here. Bailey 

 Willis thought that expansion of the rocks 

 may have been a cause in the fracturing. 

 Gilbert emphasized the fact that no appar- 

 ent cracks existed. N. H. Winchell men- 

 tioned similar phenomena in the Minnesota 

 mica schists, which apparently were basic 

 sediments. A. C. Lane recalled joints of 

 similar type but larger scale in the diabase 

 sheet of Nahant, Mass. 



Regeneration of Clastic Feldspar: N. H. 



Winchell, Minneapolis, Minn. 



The literature was reviewed and the 

 speaker's own observations given. Three 

 phases of alterations of clastic feldspars 

 occur: (1) Decay, (2) secondary enlarge- 

 ment, (3) secondary enlargement but the 

 newly added material extended so as to 

 grow into crevices between the other grains 

 of the rock. 



The Society then adjourned. 



The evening session of the Society was 

 opened at 8 :40 o 'clock in the college 

 chapel, Anderson Hall. President Charles 

 D. Walcott delivered the annual address, 

 his subject being : ' The Outlook of the 

 Geologist in America.' He reviewed the 

 work now in progress in this country, and 

 sketched a bright future for American 

 geology. 



Second day, Wednesday, January 1, 

 1902. The Council of the Society met in 

 session at Sibley Hall at 9 o'clock. 



The meeting of the Society was called to. 

 order at 9 :50 by President Walcott. The, 

 motion was made that the previously dis- 

 tributed report of the Council be accepted. 

 Carried. 



The report of the photograph committee, 

 prepared by N. H. Darton, was read by 

 the secretary. The report was accepted, 

 and the usual appropriation voted. 



Professor Dodge presented the report of 

 the auditing committee, stating that the 

 committee had examined the treasurer's 

 accounts and found them correct. The re- 

 port was accepted. The Council recom- 

 mended that the name of the western 

 section of the Society be pronounced Cor- 

 dil-ya'ran, which is the Spanish pronun- 

 ciation, used in California. The recom- 

 mendation was adopted. 



The Society then proceeded to the read- 

 ing of papers: ; 



Geology of the Snake River Plains, Idaho: 

 Israel C. Russell, Ann Arbor, Mich. 

 In the Snake river basin are many old 

 rhyolitie cones covered by lava flows of 

 later origin. The extent and thickness of 

 the Snake river lava and its relation to 

 the Columbia river lava were discussed. 

 There is a decided lack of evidence of 

 fissure eruption in the Snake river area. 

 The distinction between the cinder and 

 lava cones was illustrated, and various 

 types of lava from the flows were shovra. 



