but one circumstance of difference: the little bay abounds in shells; whereas no shells have yet been found in the mudstones of Balruddery, or the gray sandstones of the same formation, which in Forfar, Fife, and Moray shires represent the Cornstone division of the system. Ages and centuries passed, but who can sum up their number? In England, the depth of this middle formation greatly exceeds that of any of the other two; in Scotland, it is much less amply developed; but in either country it must represent periods of scarce conceivable extent. I have listened to the controversies of opposite schools of geologists, who, from the earth's strata, extract registers of the earth's age of an amount amazingly different. One class, regarding the geological field as if under the influence of those principles of perspective which give to the cottage in front more than the bulk and altitude of the mountain behind, would assign to the present scene of things its thousands of years, but to all the extinct periods united merely their few centuries; while with their opponents, the remoter periods stretch out far into the bygone eternity, and the present scene seems but a narrow strip running along the foreground. Both classes appeal to facts; and, leaving them to their disputes, I have gone out to examine and judge for myself. The better to compare the present with the past, I have regarded the existing scene merely as a _formation_--not as superficies, but as depth; and have sought to ascertain the extent to which, in different localities, and under different circumstances, it has overlaid the surface. The slopes of an ancient forest incline towards a river that flows sluggishly onwards through a deep alluvial plain, once an extensive lake. A recent landslip has opened up one of the hanging thickets. Uprooted trees, mingled with bushes, lie at the foot of the slope, half buried in broken masses of turf; and we see above a section of the soil, from the line of vegetation to the bare rock. There is an under belt of clay, and an upper belt of gravel, neither of which contains any thing organic; and overtopping the whole we may see a dark-colored bar of mould, barely a foot in thickness, studded with stumps and interlaced with roots. Mark that narrow bar: it is the geological representative of six thousand years. A stony bar of similar appearance runs through the strata of the Wealden: it, too, has its dingy color, its stumps, and its interlacing roots; but it forms only a very inconsiderable portion of one of the least considerable of all the formations; and yet who shall venture to say that it does not represent a period as extended as that represented by the dark bar in the ancient forest, seeing there is not a circumstance of difference between them?