ILLUSTRATIONS OF ISOSTATIC ADJUSTMENT 329 



an impressive distance. The readjustment from overloading a soft sup- 

 porting bed habitually is manifested in a series of diminishing waves on 

 each side of an embankment. These cases are not entirely parallel to 

 accumulations on the continental shelf, because in the latter instance the 

 gentle folds must chiefly develop on the landward side alone. Probably 

 one would go too far if one ascribed all the upheaval of folded mountains 

 to isostatic readjustment, but in appealing to the doctrine we certainly 

 turn to a true and dependable cause, as far as it is reasonably to be 

 employed. 



ISOSTASY AND OlL GEOLOGY 



The applications of geology to the location of subsurface pools of petro- 

 leum and natural gas, a use which we owe primarily to our honored Presi- 

 dent of last year, Dr. I. C. White, are all based on the identification of 

 the high points of anticlinal folds. The applications were first made 35 

 years ago to the xAppalachian anticlines of western Pennsylvania and West 

 Virginia. These folds are strong and pronounced, but in the last twenty 

 years scientifically guided exploration has spread to the Mid-continent 

 and Coastal Plain oil fields, where the anticlinal and monoclinal folds are 

 often so slight as to require instrumental surveys of a key stratum to 

 positively locate their high points. In thinking over the causes which 

 might lead to such gentle upheavals, one can not help harking back to 

 isostatic readjustment. Indeed, this suggestion has already been made by 

 M. Albertson, now of Shreveport, Louisiana. Mr. Albertson presented a 

 very interesting paper at the annual meeting of the American Institute 

 of Mining Engineers last February. It seems that he had formerly lived 

 at Cobalt, Ontario, and had observed the pumping out of Kerr Lake, so 

 that exploration for silver veins might go on safely beneath its former 

 bottom. On the bottom was a soft, slimy, and weak mud, before any 

 artificial load was contributed. Beginning with a railroad fill in 1903 

 and proceeding with accumulations of tailings from several mills and 

 with washings, hydraulicked from over 500 acres by one of the mining- 

 companies, a series of artificial deltas were produced so as really to con- 

 stitute isostatic experiments on a large scale. In the old mud of the 

 original bottom several domes of varying sizes resulted, and as the over- 

 lying load of water was pumped off the older ones grew larger and others 

 began successively to appear. Mr. Albertson acutely compares them to 

 the gentle domes of the Gulf Coastal Plain and the Mid-continent field 

 and draws the analogy between coastal sedimentation and neighboring- 

 shore upheaval. Indeed, the analogy is extremely close with isostatic re- 



