February 20, 1903.] 



SCIENCE. 



301 



the counection of this with the dynamics of 

 deformation. 



In discussion A. C. Lane inquired as to 

 the cause and amount of internal heat by 

 the planetessimal hypothesis. The speaker 

 replied that Osmund Fisher, at his re- 

 quest, had calculated that there would be 

 abundant heat developed. H. P. Reid in- 

 quired regarding the visible stratification 

 of planetessimals in the oldest known rocks, 

 and regarding the distribution of land and 

 water upon whose relations the study of 

 other planets might throw light. Professor 

 Chamberlin replied that the configuration 

 of Mars and the moon threw no light on 

 that of the earth; that the oldest rocks in 

 the Lake Superior region conformed fairly 

 well to the hj-pothesis. G. P. Merrill cited 

 the basic character of meteoric material 

 and the difficulty, therefore, of deriving 

 acid rocks from it. The speaker replied 

 that the hypothesis was not meteoroidal, 

 but nebular. That he considered meteor- 

 oidal material a negligible quantity. The 

 acidic character of the outer crust he 

 attributed to siliceoiis volcanic contribu- 

 tions. G. K. Gilbert cited the results of his 

 study of the moon as showing the effects of 

 the impact of masses falling upon it, and 

 supporting in this way the hypothesis. G. 

 F. Becker reviewed the history of the 

 nebular hypothesis, and showed that, even 

 under the new hj'pothesis, we must assume 

 an original nebula. He felt, therefore, that 

 the essentials of the old conception could 

 not be rejected. Bailey Willis made the 

 point regarding the volcanoes of the moon, 

 that they are explosive and yet on a planet 

 without an atmosphere, whereas on the 

 earth the explosions are due to steam. 

 Professor Chamberlin replied that even on 

 the earth volcanic action does not depend 

 on surface water. Its vapors come from 

 the depths. 



Block Mountains of the Basin Range Prov- 

 ince: W. M. Davis, Cambridge, Mass. 

 Observations of several of the Basin 

 Ranges in the summer of 1902 support the 

 opinion of Gilbert, Russell and others that 

 the ranges observed are carved in uplifted 

 or tilted blocks of earth-crust that had been 

 previously much deformed and eroded. 

 The faulting of the crustal blocks has been 

 continued into recent geological time. The 

 amount of erosion during the progress of 

 faulting has been so great that the pre-fault 

 topography cannot be safely determined. 

 The speaker pointed out the fact that the 

 river valleys incised in these blocks are 

 deep and narrow, the narrow gorges open- 

 ing out suddenly on the open plains ad- 

 jacent. Evidence, additional to that cited 

 by Gilbert, of the linear character of the 

 bases of the ranges, and of the triangular 

 facets terminating the ridges in front, was 

 given, — all corroborating the opinion that 

 the ranges under consideration were formed 

 by block faulting. 



Origin of Basin Banges: G. K. Gilbert, 



Washington, D. C. 



Fresh interest in the origin of the Basin 

 Ranges having been aroused by Mr. Spurr's 

 communication to the Albany meeting of 

 the society, the writer spent the summer of 

 1901 in the study of certain ranges of west- 

 ern Utah. The paper discussed the origin 

 of these as indicated by their physiography 

 and structure, and considered the nature of 

 the evidence bearing on such questions. 

 Evidence of block faulting was shown to 

 exist in the nature of extensive shear zones, 

 triangular facets terminating the ridges in 

 front, and in the even linear bases of the 

 ranges. That these faults are still going 

 on was shown by displacements in the 

 recent alluvium. On the basis of such evi- 

 dence the writer was convinced that his 

 former position regarding the origin of 

 these ranges was correct. 



