Stay, gentle reader. That craving for the grand and the sublime, that hungering after cataclysms and convulsions, that insatiable appetite for upheavals, and Titanic earth-throes, and all the mightier machinery of Nature, has done no little mischief to geology. Men have reasoned that gigantic results in the physical structure of the earth must have had equally gigantic causes operating in sublime conflict and in periodic paroxysms, now heaving a mountain chain to the clouds of heaven, now swallowing up a continent in the depths of the sea. Happily such extreme notions are fast passing away, though the old tendency in a modified form still abounds. A closer scrutiny of Nature as she actually shows herself, not as theorists fancy she should be, has revealed to us that her operations are for the most part slow, gradual, and uniform, and that she oftentimes produces the mightiest results by combinations of forces that to us might seem the very emblems of feebleness and inactivity. In place of sudden paroxysms she demands only an unlimited duration of time, and with the aid of but a few of these simple, tardy agents, she will eventually effect results perchance yet more gigantic than could be accomplished even by the grandest catastrophe. Nor in thus seeking to explain the past by defining what seems the usual mode of Nature's operations in the present, do we, as is sometimes alleged, deprive them of their high poetic element. Assuredly there is something thrilling to even the calmest imagination in contemplating the results of vast and sudden upheavals, in picturing the solid crust of the earth heaving like a ground-swell upon the ocean, in tracing amid "Crags, knolls, and mounds, confusedly hurl'd, The fragments of an earlier world;"