Geology. 557 



causes of earth movements constitute a subject not immediately 

 connected with paleogeography the doubtful use of this term 

 does not affect the conclusions of the paper. 



The other point on which difference of opinion may be held is 

 regarding a looseness in the use of the terms syncline and anti- 

 cline, a looseness which may be noted not infrequently in paleon- 

 tologic literature. 



In this paper syncline is used indiscriminately for syncline 

 geosyncline and down warp, and anticline for the contrary terms. 

 At the present time it is well recognized that synclinal and anti- 

 clinal folds are adjustments to horizontal pressure dependent 

 upon stratified structures and die out in the deeper and unstrati- 

 fied crust. Their size is determined by the competency of the 

 stronger beds to resist stress. For those broader axial folds 

 which involve the deeper crust and are generated by isostatic as 

 well as compressive forces, Dana has provided the terms geosyn- 

 cline and geanticline. For the combination of smaller folds 

 superimposed on greater, Van Hise has used the terms syncli- 

 norium and anticlinorinm, though as Rice has pointed out, his use 

 of the term synclinorium is an unjustifiable departure from 

 Dana's original definition.* For broad vertical regional move- 

 ments not clearly defined but in which horizontal thrust appears 

 to play no direct part, the physiographers have coined the terms 

 downwarp and upwarp, or arch. While the examples grade 

 toward each other, the types are markedly distinct and in paleo- 

 geography there would seem to be a gain by their clear recogni- 

 tion. To illustrate the use of these terms in their defined senses 

 it may be said that it is the subsidence of geosynclines and the 

 irregular downwarps of the negative continental elements which 

 have determined the limits of the epi-continental seas. Down- 

 warp may also be a preferable term to basin for such gentle 

 depressions without raised rims as constituted the Indiana and 

 Ohio basins of upper Paleozoic time. Usage, however, sanctions 

 in this connection the word basin, though the same word is 

 employed for intermontane depressions and the oceanic abysses. 



J. B. 



2. Virginia Geological Survey, Thomas Leonard Watson, 

 Ph.D., Director. Bulletin No. I- A. Annual Report on the 

 Mineral Production of Virginia, 1908; by T. L. Watson. Pp. 

 139, 25 figures and map. University of Virginia, Charlottesville, 

 1909. — The Report on the Mineral Production of Virginia con- 

 tains not only statistical material well illustrated by maps, but 

 also historical and general geologic information regarding the 

 occurrences of rocks and minerals of value. A further interest- 

 ing feature is the brief account of the general geology of the 

 state. The mineral products discussed are as follows : Iron ores 

 and pig iron, manganese ores, gold and silver, copper, lead and 

 zinc, coal, coke, clay and clay products, lime and cement, sand 



* On the Use of the Words Synclinorium and Anticlinorium, Science, vol. 

 xxiii, 1906, pp. 286, 287. 



