258 Scientific Intelligence. 



temperature, the temperature varying with the condition of the 

 source of the magma, its relations to the enclosing material, and 

 other causes. 



The views presented by Mr. Iddings tend to simplify greatly 

 the subject of rocks, as the author states in his concluding para- 

 graph : " The confusion which has overtaken the classification of 

 igneous rocks and the burden which is being heaped up by the 

 present tendency to multiply its terminology by creating names 

 for each modification of rock, will find their remedy in a more 

 logical conception of the true nature of the differences and rela- 

 tions of rocks." 



3. Bulletin of the Philosophical Society of Washington, vol. 

 xi, 618 pp., 8vo. Washington, 1892. — This volume, covering 

 the years 1888 to 1891, inclusive, contains valuable papers by 

 Prof. Langley, Capt. C. E. Dutton, J. P. Iddings, E. D. Preston, 



F. W. Clarke, J. R. Eastman, Everett Hayden, W. J. McGee, 



G. H. Eldridge, Whitman Cross, and H. W. Turner. 



Captain Dutton's paper " On the greater problems of Physical 

 Geography,' 1 '' relates to the earth's form, changes of level, and 

 mountain-makiug. In it he proposes (on p. 53), the term isostasy 

 for " the condition of equilibrium of figure to which gravitation 

 tends to reduce a planetary body irrespective of whether it be 

 homogeneous or not," and discusses " How nearly does the 

 earth's figure approach to isostasy?" He speaks of the theory 

 he presents as a modified form of the theory of Herschel and 

 Babbage. The effects of denudation and transportation in deter- 

 mining movement of material under the law of' isostasy are also 

 considered, and concluded to be such along coasts as would 

 shove the material of the sea bottoms landward. Mr. Dutton 

 ai'gues also that they might produce systematic plications like 

 those of the Appalachians, stating as an " important fact that 

 these systematic flexures were mainly formed at the times the 

 sediments were deposited," and that " this is a fact of geologic 

 observation." Whose "observation " is not mentioned. 



Mr. Dutton remarks that isostasy offers no explanation of 

 the great permanent changes of level ; that its very idea means 

 the conservation of profiles against lowering by denudation on 

 the land and by deposition on the sea-bottom ; that the cause of 

 permanent changes in the profiles of the land and sea-bottom, or 

 the real nature of the uplifting force, is an independent one, and 

 to him "an entire mystery." "But," he adds, "I think we may 

 discern one of its attributes, and that is a gradual expansion, or 

 a diminution of density, of the subterranean magmas. If the 

 isostatic force is operative at all, this expansion is a vigorous con- 

 sequence; for whenever a rise of the land has taken place one of 

 two things has happened : the region affected has either gained 

 an accession of mass, or a mere increase of volume without in- 

 crease of mass." The former supposes a raising of the plateau 

 against its own rigidity and its statical weight; the latter no 

 overcoming of resistance; and hence, Mr. Dutton infers that the 



