present size and form; to see how animal and vegetable life have evolved successively higher and higher forms; to see where in this wondrous drama of creation, this strange unfolding of life, the first faint, indecisive traces of man's presence are to be found; to learn what great changes in climate, in Geogony, and in life, had occurred before man's appearance, let us pass in brief review the history of early geological periods. As we have already stated, there must have been a very long period of time during which no life was possible on the globe. Of this era we know but little; for we find no strata of rocks of an earlier date than we know life, in its simplest forms, to have existed. Still we are not less confident of the existence of this era, and the mind can dimly comprehend the scene, when a nearly shoreless ocean surged around the globe. As to the extent of time during which there was no life, we have 39 no means of determining. That it was almost infinitely long is made apparent by the researches of eminent scholars on the cooling of lava. Toward the close of this extended period of time faint traces of life appear. Not life as we are apt to think of it. No nodding flowers were kissed by the sunshine of this early time. The earliest forms of flowerless plants, such as sea-weeds, and in dry places possibly lichens covering the rocks, were the highest forms of vegetable life. Animal life, if present, for the fact is denied by some, occurs in the very lowest form, merely structureless bodies, with no especial organs of sense, or nutrition: and their motion consisting simply in protruding and withdrawing hair-like processes. Such was the beginning of life. This vast period of time, which includes the beginning, is known among geologists as Archean time. From the close of this age, the history of life properly commences. It might be well to explain the means which the geologist uses to interpret the history of the globe. It is now understood that the forces of nature have always produced the same results as they do now. From the very earliest time to the present, rocks have been forming. There, where conditions were favorable, great beds of limestone, formed from shells and corals, ground up by the action of the sea--in other places, massive beds of sandstone or of sand, afterward consolidated into sandstone--were depositing. On the land surface, in places, great beds of vegetable
debris were being converted into coal. Now we can easily see how the remains of organic bodies, growing at the time of the formation of these beds, should be preserved in a fossil form. Limestone rocks are thickly studded in places with all sorts of marine formations. Coal fields reveal wonders of early vegetative growth. From sandstone rocks, and shaly beds, we learn strange stories of animal life at the 40 time they were forming. From a careful study of these remains together with the formation in which they occur, not only in one locality but all over the earth, geologists have gradually unfolded the history of life on the globe. It is admitted that, at best, our knowledge in that direction is fragmentary. This arises from errors in observation as well as that fossil formations are rare, or at least localities where they are known to exist are but few. So our knowledge of the past is as if we were examining some record from which pages, chapters, and even volumes, have been extracted. Illustration of Paleozoic Forest--------------- In consequence of this imperfect record we can not, as yet, trace a gradual successive growth from the low forms of animal and plant, life, that characterized the closing period of Archean time, to the highly organized types of the present. The record suddenly ceases and when we again pick up the thread we are surrounded by more advanced types, higher forms of life. Though we may hope that future discoveries will do much toward completing the records, we can not hope that they will ever really be perfected. So, from our present standpoint, the history of life on the globe falls naturally into three great divisions. This is no more than we might expect, when we reflect that nature's laws are universal in their action, and that the world, as a whole, has been subjected to the same set of changes. The period following on after Archean time is called, by geologists, Paleozoic time. 41 During the long course of time embraced in this age, the forms of life present wide differences from those of existing time. This period produced the great beds of coal we use to-day. But the vegetation of the coal period would present strange features to our eyes. The vegetation commenced with the lowest orders of flowerless plants, such as sea-weeds; but, before it was brought to a close, there was a wonderful variety and richness of plants of the flowerless or Cryptogamic division. In some of the warmest portions of the globe, we have to-day tree-ferns growing four or five feet high. During the closing part of the Paleozoic time, there were growing all over the temperate zone great tree-ferns thirty feet or so in height. Some varieties of rushes in our marshes, a foot or two in height, had representatives in the marshes of the coal period standing thirty feet high, and having woody trunks. Near the close of the Paleozoic time, vegetation assumed a higher form of life. Flowering plants are represented. Pines were growing in the coal measures. In animal life a similar advance is noted. The class of animals having no backbone, or invertebrate animals, were largely represented. But, toward the close of the Paleozoic time, we meet with representatives of the backbone family. The waters swarmed with fishes. Besides these, there were amphibians; and reptiles in the closing portions. Illustration of The Pterodactyl.-------------- Thus we see what a great advance was made in life during this period. The forms of life during the early stages of this age were inferior in 42 this, also, that they were all water species. But, before it closes, we have a rich and varied terrestrial vegetation, and also air-breathing animals. The class Mammalia, to which man belongs, had no representative on the earth during the extended Paleozoic time. We can easily see, from the foregoing, how appropriately this period has been named that of old life forms. In imagination we can recall a scene of this old age. The air is sultry and full of vapors. The soil seems hot and steaming. This is a veritable forest, but we see none of the beautiful flowers which we associate with tropical vegetation to-day. In the branches of the graceful tree-ferns, we will look in vain for birds. They were yet far in the future. Neither were there any of the higher orders of animals present. Not a single representative of the great class of mammals enlivened the depths of the forest. There were fishes in the waters, but not the fishes of to-day. Some true reptiles and amphibians disported themselves in swampy jungles, but they were unimportant. Almost the only sound to break the stillness, was the hum of marsh-loving insects, the whistling of the wind, and the roar of the tempests, which we may well believe raged with the more than tropic severity of the present. The time at last came for the dawning of a new era. Vast changes had been taking place in the geography of both continents. The region to the southwest of the Green Mountains was upturned. The Alleghany Mountains were formed, and the region east of the Mississippi River became part of the stable land of the continent. In Europe, nearly as great changes occurred. The conditions of life must have been greatly modified by these geographical changes. The life-forms bear testimony to this changed condition. Old forms die away, and are succeeded by those 43 approaching more nearly our own times. The name of this period is the Mesozoic time, or the period of middle life forms. It is instructive to notice the steady advance in the type of life, both animal and vegetable. The abundant flowerless vegetation of the coal formation of the preceding epoch dwindles away. But the flowering trees increase in number and importance until, in the closing period of Mesozoic time, we have trees with deciduous leaves. A great many of our forest trees had representatives in the forests of that epoch. Illustration of Ichthyosauri.----------- Palms and species like the big tree of California were growing side by side with species akin to our own common trees. But in the animal world there were many strange forms. This was the age of reptiles. They domineered on the land, in the air, and in the sea. On the land there stalked huge reptiles fifty and sixty feet long, and, when standing erect, at least thirty feet high. Some of these huge creatures were carnivorous, living on other animals. Others fed on the foliage of trees. In the air, huge reptilian bats, veritable flying dragons with a spread of wings from ten to twenty feet, disported themselves. In the sea there swam great reptilian whales, seals, and walruses. There was a marvelous abundance of reptilian life. At the present day, there are not more than six species of reptiles in the whole world having a length of over fifteen feet, and not more than eighteen species exceeding ten feet in length. But from one limited locality, representing but one era of this age in England, there have been discovered four or five species of carnivorous reptiles twenty to fifty feet long, ten or twelve species of crocodiles, lizards, and swimming 44 reptiles from ten to sixty feet long--besides multitudes of great flying reptiles and turtles. Doubtless similar scenes of animal life were everywhere represented. Illustration of The Labyrinthodon.-------- Birds made their first appearance during the Mesozoic time, and here we obtain a clear view of nature's methods of work. There is no longer a doubt but that the first birds were simply
