52 



SCIENCE. 



[N. S. Vol. III. No. 54. 



The principal object of this paper was to 

 show that the drainage of the Appalachians 

 constitutes a record of Mesozoic history, 

 and that this record is to the physiographer 

 of equal importance with that contained in 

 the forms sculptured from the surface of 

 the land. 



In the discussion President Shaler took up 

 the relations of the drainage systems of 

 Kentucky and emphasized the value of the 

 paper in helping to clear away points 

 that were previously obscure. Eemarks by 

 Messrs. Davis and Gilbert followed, and the 

 latter in reply to a question alluded to the 

 part played by the rotation of the ear th in 

 determining lines of drainage. He de- 

 scribed it as slight, if at all present, and as 

 requiring almost unattainable delicacy of 

 tests for its detection. 



Some Fine Examples of Stream Rohhing in the 

 Catskill Mountaiiw. N. H. Darton, 

 Washington, D. C. 



By means of a large topographical chart 

 the speaker showed how the Kaaterskill 

 and Plaaterskill Creeks flowing eastward 

 into the Hudson, had pushed their divides 

 backward until they had robbed the head- 

 waters of Schoharie creek. Other smal 

 ones along Esopus creek were also cited. 



Movement of Eoelcs Under Deformation. C 



R. Van Hise, Madison, Wis. 



The paper was a general discussion of the 

 behavior of rock when subjected to deform- 

 ing stresses, and is preliminary to the dis- 

 cussions which the author gave last summer 

 on the analji^sis of folds and upon the rela- 

 tions of primary and secondary structures 

 in rocks. 



Three zones in the earth's crust were 

 cited: 1, an outer one of fracture during 

 rock movement; 2, an inner one of mixed 

 fracture and flowage; 3, an inmost one of 

 flowage. In elaborating these, the effects 

 of pressure on rocks were analyzed. It was 

 shown that a quick application of pressure 



might fracture where a slow one would 

 cause flowage, and that the possible depth 

 at which cavities might exist was greater 

 than had been assumed by Heim (.5000 m.). 

 Mathematical deductions by Prof. Hoskins, 

 of Stanford University, made for this paper, 

 have shown that where the walls of a cav- 

 ity are subjected to three equal stresses at 

 right angles with one another, the cavity 

 will be closed up in case the stresses equal 

 two-thirds the ultimate strength of the rock. 

 With a single stress the full crushing pres- 

 sure is needed. Assuming the strongest 

 rock for these conditions in order to get a 

 certain maximum depth below which cavi- 

 ties would be an impossibility, and taking 

 the specific gravity of the crust at 2.7, from 

 which in the calculation we must subtract 

 1, for the water that penetrates all fissures, 

 we obtain for the first relation of forces 

 6670 metres and for the second 10,000 

 metres as this depth. Under these con- 

 ditions the water is understood to be free to 

 escape. Instances of quartz pebbles were 

 cited, one being rolled out without fracture 

 in the Marquette region. The eflects upon 

 heterogeneous rocks were discussed and 

 their relations to folding. The zone of 

 mixed crushing and folding was next taken 

 up, after which the paper concluded. In 

 the discussion A. C. Lane spoke of the 

 bearing of the paper on the conceptions ad- 

 vanced by him at a previous meeting re- 

 garding the escape of the earth's internal 

 gases. J. F. Kemp referred to its impor- 

 tant bearing on the origin and possible 

 depth of formation of mineral veins. B. 

 K. Emerson cited the case of the Cambrian 

 gneisses of Massachusetts, in which quartz 

 crystals are rolled out as thin as paper, but 

 with their optical properties unimpaired, 

 and emphasized the possibility of chemical 

 recrystallization. J. P. Iddings brought 

 up the interesting experiments of O. Miigge 

 on ice crystals as recently set forth in the 

 Neues Jahrbuch, showing that ice sheared 



