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show under test greater strength, greater rigidity, and a higher elastic 

 limit, than the original sandstone. A plastic shale, if duly forced to "fail" 

 often enough and sufficiently, might, like certain of our shopmen, come 

 out of the process a highly elastic schist. If ten million blocks of earth- 

 material, so distributed throughout the earth as best to represent its struc- 

 tural competency, could be tested today and the results compared with a 

 similar test made in Cambrian times, the elastic competency would quite 

 certainly be found to be as great now as then. There is some presump- 

 tion that it wovild be rather greater. 



The engineer in dealing with an artificial structure properly enough 

 proceeds on the assumption that there is present a certain modicum of 

 structural competency, and that when this is once broken down that ends 

 the matter. The earth cannot be dealt with advisedly in this way. The 

 constant regeneration of strength, of rigidity, and of elasticity, under 

 appropriate conditions, is as vital a factor in the earth problems as is the 

 breaking-down of such acquisitions of these properties as had been inherited 

 from the previous constructive processes. 



There are many things in the address which are suggestive and helpful, 

 and in so far as they lead on to more critical studies they are heartily to 

 be welcomed. The reviewer would suggest, however, as a running mate 

 to this address, one on the earth as a generative structure. T. C. C. 



Schmidfs Geological Sections of the Alps: 



American geologists who are interested in modern interpretations of 

 Alpine structure will find a valuable series of colored sections in several 

 pamphlets by Professor C. Schmidt of Basel, as follows: (i) Bild und Bau 

 der Schweizeralpen, which appeared as a supplement to Vol. XLII of the 

 Swiss Alpine Club, 1907 (Basel: Finckh. Fr. 5), contains, besides a 

 beautifully illustrated text, a small geological map and a remarkable group 

 of sections illustrating the extreme extension now given to the idea of 

 overthrust folds. (2) Fiihrer zu den Exkursionen der deutschen geologischen 

 Gesellschaft im siidlichen Schwarzwald, im Jura und in den At pen, August, 

 igoj, by Schmidt, Buxtorf, and Preiswerk (Stuttgart: Schweizerbart. M. 5), 

 containing a number of more detailed sections, as well as the group of 

 general sections. (3) JJeher die Geologie des Simplongebietes und die 

 Tektonik der Schweizeralpen (Eclog. geol. Helv., IX), with a number of 

 detailed sections and a general geological map of the Alps between St. 

 Gotthard and Mont Blanc. (4) Tektonische Demonstrationshilder (to be 

 had of the author. Fr. i), with some of the same Alpine sections and 

 several additional sections for the Vosges and the Schwarzwald. 



W. M. D. 



