202 THE POPULAR SCIENCE MONTHLY. 



of fuel, we must increase our outlay of capital. So long as coal was 

 cheap, it may have been better worth the while of the individual con- 

 sumer to employ coal wastefully rather than spend money upon the 

 arrangements for economizing heat. On the other hand, when coal is 

 dear, the daily expense from the waste of fuel will induce a capital 

 outlay to secure economy of heat. Journal of the Society of Arts. 



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THE DKIFT-DEPOSITS OF THE NOETHWEST. 



By N. H. WINCHELL, 



STATE GEOLOGIST OF MINNESOTA. 



I. Nature of the Drift. 



IN the March number of this journal, Mr. Elias Lewis calls atten- 

 tion to the occurrence of bowlder-like masses of clay in strati- 

 fied gravel, at Brooklyn, N. Y. In the progress of the geological sur- 

 vey of Ohio, similar masses of gravelly clay were met with in the 

 northwestern portion of the State, lying in the stratified gravel and 

 sand that constitute the long ridges which have often been pronounced 

 " lake-beaches." These occurrences, and a great many others that 

 militate against the popular theory that those ridges are attributable 

 to the action of the waters of Lake Erie, and the stratification of the 

 drift generally over the "interior continental basin" to the action of 

 a wide-spread lake, or of the ocean, made it necessary to reinvestigate 

 the drift-deposits thoroughly, for the purpose of deducing from the 

 drift itself such a theory of its origin as would stand the application of 

 all the facts. Such reexamination has resulted, in the ojfinion of the 

 writer, in the confirmation of the glacier theory of Prof. L. Agassiz, and 

 the consequent abandonment of the iceberg theory of Peter Dobson. It 

 has also shown the baselessness of the assumption of some who would 

 extend the Champlain epoch of Prof. J. D. Dana, so as to bring on, 

 after the period of the glacier, a submergence of the continent beneath 

 the ocean. It is proposed to review, in a non-technical way, the phe- 

 nomena of the drift of the Northwest, and to offer a few thoughts on 

 the glacier theory, and its application to the explanation of those phe- 

 nomena. 



In general, the term drift applies to whatever lies on the surface 

 of the rocky framework unconsolidated, whatever be its origin or 

 lithological character. Glacial drift is that which has been transport- 

 ed by the agency of ice, or by ice and water, from regions farther 

 north, and spread over the surface of the country. It may embrace 

 bowlders, gravel, and clay. These substances may be arranged in 

 stratification, and nicely assorted, or they may be confusedly mixed. 



