Januarys], 1898.] 



SCIENCE. 



83 



iihe cylinders dropped snugly in and were 

 oaught midway of the spool. The cylinders 

 •of marble were about two centimeters in 

 diameter. Chrome-steel plungers were em- 

 ployed in the squeeze, and fitted perfectly 

 in the spools. By using the city water 

 mains, which give at the University a 

 3)ressui'e of 135 pounds to the square inch, 

 ■oil was forced in beneath the piston of 

 the press, and cylinder pressure gauges 

 :and a recording curve-tracing mechanism 

 were connected. The blocks were grad- 

 Tially compressed until subjected to thirty 

 tons' pressure. Under this squeeze the 

 marble cylinder bulged at the middle, 

 ■expanded its iron jacket and approxima- 

 ted a thick disc. When released it was 

 found that it had flowed without losing its 

 ■cohesion at all. When split down the ver- 

 tical axis the cross section revealed two 

 opposing paraboloids, or blunt cones of un- 

 changed marble, filled in between with a 

 dense, chalky variety, but all perfectly solid. 

 Thin sections show a great abundance of 

 twinning striations and gliding planes and 

 -evidences of strain. Cylinders of Baveno 

 granite are now ready for experimentation, 

 but have not yet been compressed. Peat 

 has, however, been compressed into a black, 

 shining and lustrous substance, very like 

 high-grade lignite or coal, a result similar 

 to that obtained abroad. Copper filings 

 have been compacted also to solid metal. 

 A further apparatus has been designed so 

 tliat superheated steam can be introduced 

 into the test, which can be kept at 500° F., 

 for months at a stretch, while the compres- 

 sion is progressing, the gauges and recorder 

 meantime registering the pressure at all 

 times. Dr. Adams stated that two and 

 a-half years had been spent in experimenting 

 and six months in getting results. 



The Fellows were outspoken in their 

 praise of this work, and it was felt by all 

 ^;o be one of the most important contribu- 

 tions ever laid before the Society. It brings 



within the domain of experiment some of 

 the obscure proceses of dynamic metamor- 

 phism and throws great light on the viscous 

 flow of rocks. 



The Geological versus the Petrographical Classi- 

 fication of Igneous Rocks. Whitman Cross, 

 Washington, D. C. 



In this paper the aim was to show that 

 much of the confusion in existing schemes 

 for the classification of igneous rocks arises 

 from wrong ideas as to the relations of 

 petrography to geology. Suggestions were 

 made which it is hoped will be useful both 

 to the geologist and to the petrographer. 



Dr. Cross presented a very thorough and 

 philosophic review of the vexed question of 

 nomenclature and classification. The dis- 

 tinction was made between petrography, 

 the descriptive part of the subject, and 

 petrology, the discussion of the at present 

 more or less hypothetical or theoretical 

 views regarding the splitting and variations 

 of magmas, etc. Although no actual scheme 

 was suggested, the general bearing of the 

 paper tended toward the development of 

 one that should give widespread satisfac- 

 tion. 



In discussion J. F. Kemp emphasized the 

 importance of having the larger groups of a 

 petrographical scheme, ones that can be 

 used by the student, the mining engineer 

 and by others engaged with rocks, whereas 

 the finer determinations under these gen- 

 eral, working groups might be left to the 

 specialist. Such groups must depend solely 

 on mineralogy and texture. 



On the Classification of Igneous EooJcs. Jos. 



P. Iddings, Chicago, 111. 



The paper involved a discussion of some 

 general principles of classification with 

 special reference to the chemical composi- 

 tion of rocks. The point of greatest inter- 

 est in the paper was the extremely signifi- 

 cant charts that Professor Iddings had 

 prepared on the basis of over 900 analyses. 



