The determination of time-relations has been based chiefly upon aqueous deposits. Attention is now turning more than heretofore to the study of topographic forms as time indices and as means of correlation. The doctrine of baselevels opened the way to specific studies of land sculpture as a means of determining successfully the varying attitudes of the land and their accompanying time-relations. A considerable body of discriminating geologists have become enthusiastic workers in this new field, and are bringing forth results of great interest and value. It becomes evident, upon consideration, that if it is possible to correlate fragments of topography distributed over the face of the continent, we may connect formations at great distances by a physiographic chain, where sedimentary connection is entirely wanting. Many unsolved problems in correlation will yield to the application of the new method, and many tentative correlations will be overthrown by it.
The method has . . .