AMERICAN GEOLOGY DECADE OF 1840-1849. 375 



igneous masses only, and hence his periods those of igneous intrusion. 

 To the then ordinarily accepted causes of folding, elevation, and 

 depression, as steam and elastic vapors in a high state of tension, the 

 contraction of the earth by secular refrigeration, or the undulatory 

 action of the fluid interior, combined with tangential force — Mather 

 added a fourth. He conceived that, as the earth is a cooling and 

 shrinking body and revolving with increased rapidity owing to its 

 diminished diameter, the ocean, being fluid, would not immediately 

 partake of this increased velocity, and, therefore, as the earth revolved 

 from west to east, a current of greater or less strength would set to 

 the westward over the whole ocean, but strongest at the equator. The 

 inertia of the solid mass of the interior of the globe would also cause 

 it to press to the westward with a power dependent upon the rapidity 

 of rotation. Given, then, lines of weakness where yielding would 

 take place, motion and distortion or elevation might follow. If the 

 interior were fluid and the solid exterior floating upon it. a change in 

 the velocity would produce still stronger effects and changes of lati- 

 tude of masses of the earth's surface affected in this way would result. 

 Evidences of this were seen in the wrinkled and folded strata. 



Some 75 pages of Mather's report were given up to a description 

 and discussion of the phenomena of the drift. He concluded that the 

 transport of the drift and the production of scratched surfaces were 

 contemporaneous, the drift itself being transported in part by cur- 

 rents and in part by ice, itself drifted by the currents. The period of 

 the drift and that of the Quaternary deposits were separated by a 

 partial submergence of the land; and further, the periods of the drift 

 were periods when the currents were stronger than at the present 

 time. He conceived this to be due to a collapse of the crust of the 

 globe upon its nucleus by refrigeration, causing an acceleration of the 

 velocity of rotation, "and this a consequent disturbance of the form of 

 equilibrium of the spheroid of rotation, which would be compensated 

 by the flow from the polar regions and an accelerated flow of the 

 equatorial regions/' This sudden acceleration of the ocean currents 

 he felt would be sufficient to cause the transportation of vast quanti- 

 ties of detritus-laden ice from the polar regions southward. 



The large amount of drift scattered over the central and northern 

 Mississippi region he ascribed incidentally to ice-laden currents from 

 Hudson Bay and the polar seas which, flowing over the northern part 

 of the United States, would be met by the warm waters of the Gulf 

 Stream, causing them to deposit their loads. The warm current flow- 

 ing northward would be superimposed on the cold current, the latter 

 continuing southward beneath it, transporting the finer materials such 

 as now occupy the lower Mississippi Valley. It ma}^ be added that 

 Mather's disposition to overload and overwork the Gulf Stream is 

 somewhat amusing. Not merely did he ascribe the glacial drift and 



