Febkuary 10, 1905.] 



SCIENCE. 



219 



himself. The author has devised a piece of 

 apparatus which mechanically illustrates 

 his theories in a remarkable manner. Pro- 

 fessor E. H. Kraus, in a paper on the 

 origin of the caves of the island of Put-In 

 Bay, Lake Erie, stated that in all prob- 

 I ability the folding of the Lower Helder- 

 berg limestone of the region was caused by 

 hydration of anhydrite, since large de- 

 posits of gypsum have been encountered in 

 sinking wells in the immediate vicinity. 

 The increase in volume caused by such 

 hydration may be as high as sixty per cent, 

 and the energy developed in the process 

 would be sufficient to account for the re- 

 sults observed. Subsequent leaching out 

 of the gypsum by percolating waters would 

 account for the existence of the caves, and 

 the collapse of the roofs of the cavities 

 would account for the step-like form of the 

 ceiling. 



Mountain growth and mountain struc- 

 ture was the subject of a communication 

 from Mr. Bailey AVillis, of the United 

 States Geological Survey. The study of 

 peneplains at various altitudes with refer- 

 ence to sea level, in North America and 

 Eurasia, demonstrates that elevations of 

 the earth's surface have resulted from 

 deformation which produced warping of 

 previously levelled-off surfaces. In gen- 

 eral this process has been a recent one, 

 post-Mesozoic in time, and it may be held 

 that mountains are youthful features of 

 the earth. The structures which have been 

 discovered in mountain masses are such as 

 are developed under a considerable load, 

 and consequently at notable depths in the 

 earth's mass. Study of the relation be- 

 tween structure and form leads to the con- 

 clusion that modern mountains are not the 

 effects of the forces which produce the 

 structure, a conclusion which cuts at the 

 foundation of older systems of classifica- 

 tion. 



Professor Florence Bascom, of Bryn 



Mawr, brought out by means of detailed 

 maps the nature of the formation and the 

 structure of the Piedmont region of Penn- 

 sylvania, giving the results of extended 

 field work carried on for the United States 

 Geological Survey. Her paper was fol- 

 lowed with one on the Piedmont of Mary- 

 land in correlation with that of Pennsyl- 

 vania by Professor E. B. ]\Iathews, of 

 Johns Hopkins University. The latter 

 author afterward read a paper on the 

 Cockeysville marble, in which he gave the 

 results of much very close field study by 

 himself and W. J. Miller, of Baltimore, 

 into the concrete problem in Piedmont 

 structure, the area concerned occupying 

 approximately 300 square miles and lying 

 north of the city of Baltimore. 



Mr. N. H. Darton, of the United States 

 Geological Survey, in discussing overlap 

 relations along the Rocky Mountain front 

 range, described features which have been 

 traced by him through Wyoming and Col- 

 orado into New Mexico, mainly for the pur- 

 pose of correlating the different forms. 

 He finds that the Paleozoic and Mesozoic 

 rocks of the region present frequent varia- 

 tion in character, occurrence and varieties. 

 In the course of his field work, Mr. Darton 

 visited the Zuni salt lake, forty miles north 

 of the Indian pueblo of Zuni. At this 

 locality there is in the plain a circular 

 depression about a mile in diameter, con- 

 taining a salt lake and two cinder cones. 

 The depth of the depression is about 200 

 feet and its walls are of Cretaceous sand- 

 stone, capped on one side by a lava flow. 

 All around the rim there is a wide low 

 ridge of volcanic ejecta which has been 

 laid down in water. The history of this 

 remarkable feature is not clear. 



Professor Frank C. Adams, of McGill 

 University, presented the results of an in- 

 vestigation made by himself and Mr. E. J. 

 Coker into the cubic compressibility of 

 rocks and certain phases of rock flow. The 



