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palm, called Cycads, was introduced during the course of that era. After its close the conditions of life in the air were much changed.

The composition of the air was now different. The first mountain-making period came on, and probably the climate was very materially changed in temperature thereby, for raising the land lowers the temperature of the air.

It was indeed a long time before the mountain-making was complete, but that accomplished, all the circumstances had become so entirely different that the old vegetation which could not accommodate itself to the new relations died out; but it was still longer before distinctively modern forms became the ruling feature.

Accordingly, the first series of rocks after those of the coal formation still show a strong likeness in vegetable forms to those of the coal period. In the first two eras of the Mesozoic that follow this first series--called, the Permian-the conebearing species of trees increase and grow more modern, and most of the older families represented in the coal-beds disappear; but in the last of the three eras of the middle period the forms now existing were very largely represented. For the first time oak, maple, willow, and other representative forest and fruit trees appear. As animal life, large and small, in forms similar to the present, began to abound on the land, among which were birds, we may suppose that the seed-bearing grasses were also introduced in that period.

In the Tertiary there was a vast increase in the variety and modern character of the vegetable forms. It is probable that the Upper Valley, far west of the Mississippi, and even of the Missouri, was covered with vegetation more or less luxuriant, for a sub-tropical climate reigned even far up toward the pole. The rose, the whortleberry, and various other flowering shrubs of that period have been found. The earth began to deck itself in all the beauty of our present warm regions, and insect life swarmed among the flowers. The modern era in plant life had fully opened.

Thus we find that the lowest forms of the lowest class of vegetable life were early developed in the most ancient seas and probably in extraordinary abundance; that lichens and mosses probably soon came to cover the early continents to which all the higher classes of the lowest division of plantsthe flowerless Cryptogams-were added as the coal period approached. The cone-bearing trees were also introduced before the age of coal. They were the only representatives of the Phenogams or true seed-bearing plants, and, indeed, the first true trees of ancient time. The Cycads were added in the latter part of the coal era. These were Phenogams, in form resembling palms, but fruiting like Conifers. These were both among the lowest of the higher division of plants.

Ferns, Conifers and Cycads chiefly ruled the Middle Period, although the more perfect modern trees and plants came in before its close. The Middle Period is called, botanically, the "Age of Cycads," for they were then extremely numerous, but steadily diminished in its closing ages until in modern times there are comparatively few and these are confined to tropical regions. With Cenozoic time were rapidly introduced the most perfect vegetable structures to supply the wants of ripening animal life.

The part vegetable life has played in the processes of storing the Great Valley with materials eminently serviceable to man has been therefore large and most important. The best and largest supplies of iron, the vegetable kingdom has assisted to accumulate. It furnished the base of supplies to the animal life that has produced near two thirds of the rock in the Valley-the limestones-and, in some minute forms, called Diatoms, formed rock of considerable extent. It has supplied much of the petroleum and all the coal with which the Valley is made so eminently rich, and has crowned its long list of great services by furnishing a surface soil of unrivalled depth and value over the most of the wide-spreading bowl. Its modern forests, since the Glacial period especially, prepared

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the country for primitive man, and give to civilized man no small store of wealth.

That the vegetable and animal kingdoms form the two harmonious sides of one system of life is, finally, noticeable in this, that the life force in animals uses the oxygen of the atmosphere as the chemical agent for preparing its building material and rejects carbonic acid gas; while in vegetables the contrary is true, oxygen being rejected and carbonic acid gas being stored in the form of woody fibre.

CHAPTER VI.

ANIMAL LIFE IN THE VALLEY, ANCIENT AND MODERN.

The Life Force gained many and important ends in the comparatively narrow limits of the Vegetable Kingdom. In the plan of animal life several principles appeared that vastly raised this class in the scale of being, and left open the most wonderful possibilities to progress. In the very lowest animals there was a feeble dawning of a new individuality in sensation, in intelligence, and in the power of self-control. At the first there was but the faintest glimmer of these, and sometimes they were not all united in the same animal. It is sometimes very difficult to tell whether a structure is vegetable or animal, so slight is the space that separates the most sensitive organization among plants from animals having the least vitality.

But sensation was to be gradually developed until it became exquisitely perfect in the elaborate nervous system of the highest sub-kingdom of animals; the capacity of self-motion was to increase into the most remarkable powers of voluntary physical force; and intelligence was to ripen until most phases of the supreme mental attributes and capacities of man had been shadowed forth more or less completely, though in every case fragmentally and in limited development; and, finally, by a vast leap, all these qualities of intelligence, freed, as to the race at large, from definite limitations, were to be concentrated in the Ideal Animal.

There is a world of suggestive mystery in the gradual development of the animal frame until some of the animals came to possess physical parts closely resembling man's; and a still greater mystery is the instinct and intelligence so like, and so

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unlike, man's bestowed on the different classes of animals. In each animal these higher gifts are very perfect so far as the special ends of its life can be served by them. There they cease. A single strongly marked quality belongs to each race with all the intelligence necessary to a successful career in such a character. There the resemblance ceases. The animal has no such reserve of unused powers and unlimited capacity of development, in a thousand ways, as are seen in man. There is a breadth and reserve of force in the higher qualities of the man that destroy the idea of his true and close relationship to the animal world. The most intelligent animal has but the shadow of the man's mental compass outside the range of its physical instincts. It is often a dense shadow, but, in the end, is nothing more. What mystery of origin and destiny lies behind these real physical, and instinctive and shadowy mental, relationships? What is man that immeasurable geological time should labor so strenuously and constantly for him, and that all organized nature should bear the broken and shadowy fragments of his image?

There are five great types or divisions of animal life, regarded as to the plan of their physical structure-Protozoans, Radiates, Mollusks, Articulates and Vertebrates. The first four are called Invertebrates. Most of the larger and more important and perfect animals belong to the last class-Vertebrates. The lowest class, Protozoans, are very simple, almost formless and jelly-like in structure, with no nervous system, often no mouth or stomach or permanent limbs. Whenever these are required they are extemporized for the occasion. They are usually extremely minute. They are commonly inclosed in a shell, and the substance of the animal is protruded to secure food. The lowest class of these are believed to have been introduced the first of all animals, although the absolute proof seems, as yet, wanting.

The Radiates are formed on the plan of a flower, similar parts spreading from a common center. They are very often