330 J. F. KEMP ISOSTASY ANT) APPLIED GEOLOGY 



adjustment. We have the pumping out of the water, analogous to the 

 removal of load by erosion. We have the introduction of tailings and 

 debris in small deltas. We have finally the bulging in domes because of 

 slow, subsurface transfer of plastic material, the domes rising at a modest 

 distance from the deltas. Change the scale to that of nature and we have 

 a very suggestive series of observations. 



When we find isolated domes, or short anticlines with relatively small 

 axial length, or upheavals caused by the upward flowage of relatively 

 plastic rock-salt, we can not help surmising that the pressure from coastal 

 overloading has been transmitted by deep plastic flow and has produced 

 the bulges. Except for this cause, localized upheavals are difficult to 

 explain otherwise than by igneous intrusive masses, probably laccolithic 

 in shape. 



I.SOSTASY AXD FAULT PrODUCTIOX 



The slow, viscous flow of rock-matter near or just below the 71-mile 

 limit, or in the asthenic zone of Barrell, can not well take place in great 

 volume without transmitting strains to the upper world. Possibly the 

 faults which are so often the locus of mineral veins, and especially of 

 veins not visibly or apparently connected with igneous intrusions, may in 

 some way be connected with these interior transfers. Possibly, also, the 

 much greater number of faults which, as we are daily learning with 

 greater and greater emphasis, are associated with many of our striking 

 topographic features may also be caused by these transfers. 



Mineral Veins and entrusive igneous Masses 



The greater number of mineral veins, and especially those productive 

 of ores, are now pretty well recognized to be associated with igneous in- 

 trusive masses. What we geologists who have from time to time to deal 

 with them, or with the associated intrusive bodies, wish to know is some 

 reasonable explanation for the uprising of the batholiths or laccoliths or 

 sills or dikes from the depths. If the slow, deep-seated, viscous flow of 

 rocks still solid, but yet highly heated, sometimes turns from horizontal 

 movement to a journey upward, then we can understand that with dimin- 

 ishing pressure the vast masses may fuse, may finally come to rest within 

 a moderate distance from the surface, and may part with dissolved gases. 

 We shall thus have a reasonable explanation of a train of events one of 

 whose end products is the mineral vein. If isostatic readjustment will 

 furnish us with this extremely important fundamental conception, it will 

 do us great service. The heavy deposition of sediment, perhaps at a re- 



