RECENT, or lIumAN PERIOD, in geology, is the title given to the epoch that has elapsed since man made his appearance on the globe. The causes that operated through out the ages of geological time to produce the changes recorded in the various sedimen tray deposits, did not terminate with the beginning of human history, but have been ever acting since man was able to observe and to record his observations, and are still in progress around us. The solid earth is being washed away by atmospheric agency, and the abraided portions are continually carried away and imperceptibly by streams and rivers, to form new deposits in the depths of inland lakes or of the ocean. 'Vol canoes are throwing up lava and seorite, and earthquakes are elevating portions of the earth's surface in one place, and depressing them in another; and plants and animals are, either with their living bodies, or their dead exuviw, forming, as in past ages, deposits in various places, as in the foraminiferous ooze of the deep ocean, and the enor mous coral reefs of the eastern seas. or the peat-mosses and diatomaceous earths of tem perate climes. The record of all these changes, and the remains of man and of the plants and animals which the strata produced by them contain, have for some years received great attention. As they form common ground for the antiquary and geologist, they have been diligently investigated by the students of both sciences. The classifica tion adopted for the subdivision of the recent period is based on what is supposed to have been the progress of human civilization. The first rude inhabitants of a country seem to have been acquainted only with stone implements. Their hammers, knives, and spears were made of stone, sharpened by chipping the edges, and subsequently by grind ing and polishing. In Denmark, these stone implements are found buried in peat mosses, associated with the remains of plants and animals that still live in that or neigh boring countries. The common tree in these mosses is of Scotch fir, which has not been a native of Denmark during historical times. Of the same age are the " kitchen-mid dens," found on the coasts of the Danish islands in the Baltic. They are mounds of the shells of the oyster, cockle, periwinkle, and other edible mollusca, like those formed by the North American Indians on the eastern shores of the United States. The imple ments found in them are formed of stone, sometimes of wood and bone, but never of me:al. Similar "middens" have been described as occurring in various places in the a_
of Scotland. The people who built the earliest of the lacustrine habitations of Switzer land were also unacquainted with the use of metals. See CRANNOGES. The paucity or almost absence of human bones in such early deposits, whether in Denmark or Switzer land: is attributed by antiquaries to the supposed practice of burning the dead.
While the lower portion of the Danish peat-mosses is characterized by the presence of stone implements and the trunks of Scotch fir,. the upper portions of the same mosses abound in trunks and acorns of the common oak, and with these are associated imple ments and articles of bronze. In many of the Swiss pile buildings, the bronze imple ments also supplanted those of stone. The various articles exhibit a considerable advance in civilization, as is to be expected from the using a metal, the possession of which implies the existence of foreign commerce, since tin was in ancient times billy obtained from Cornwall.
In progress of time, the oak in its turn disappeared from the surface of Denmark, and was followed by the beech, which still continues to flourish luxuriantly in Denmark. The use of bronze also gradually gave way before the now discovered iron. A few of the lake buildings seem not to have been abandoned until after the inhabitants became acquainted with the use of iron, as some articles made of this metal have been found at Nidau.
While it is useful thus to characterize the various steps in the civilization of man, and to associate them with the strata in which they occur, it would be a source of end less error to suppose that all such strata are contemporaneous; for the various ages have really existed at the same time not only in different countries-of the world, but even in contiguous regions, and probably implements of the three materials have been used at the same time by different inhabitants of the same district. See BRONZE, AGE OF'. The occurrence, then, of stone implements in several deposits exhibits not a similarity of age, but a similar stage of advancement in civilization, consequently no dependence can beplaced on those calculations which trace back the iron, bronze, and stone periods as if they had preceded each other in regular chrouolcigieal series, and each had occupied a given number of years.