Page:Popular Science Monthly Volume 3.djvu/212

202 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 consumer 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.



I. Nature of the Drift.

N the March number of this journal, Mr. Elias Lewis calls attention to the occurrence of bowlder-like masses of clay in stratified gravel, at Brooklyn, N. Y. In the progress of the geological survey 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 reëxamination has resulted, in the opinion 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 phenomena of the drift of the Northwest, and to offer a few thoughts on the glacier theory, and its application to the explanation of those phenomena.

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 transported 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.