Leaf by leaf the great book of nature was turned, and the story found to be marvellous beyond any conception of poet or romancer. To the common eye the surface of the earth, with its wide diversity of mountain, valley, ocean, and plain seemed wonderful enough, but the geologist looked deeper and found still more enchanting scenes. Like a magician of old he bade the earth lay aside her green veil of mystery, and claimed her secrets for his own.

He examined the rocks and found that the white cliffs of England were the products of living animals, and that the tiny shells, pieces of coral, fragments of sponges, and other fossils found in limestone or chalk rocks, indicated clearly the sources of formation, and pointed to a time when myriads of animals swarmed in the seas where now stand the long ranges of hills that give beauty to the land.

He looked at the great coal measures of and America, and read in their records even more wonderful accounts of the time when the continents were clothed in verdure to the shores of the Arctic seas; imprinted in the dark layers of coal he saw the plume of the fern, great tree—ferns that towered like palm—trees, resembling species now found in tropical regions; while other forms, such as large cone—bearing trees resembling the pines, and trees of a type that has now disappeared from the earth, having the whole surface of the bark covered with leaves thickly set like scales, gave greater evidence of the abundant vegetation which gave grace and beauty to those far—off ages.

Then the zoölogist added his gifts of fossil animals, and it was found that the earth was full of the remains of ancient life, and that from the skeleton of the great mastodon, whose tread would trample down the trees of the forest, to the tiny leaf imprisoned in a crystal drop of amber, all could contribute to the story of the earth and make its meanings clearer.

But, while geologist and zoölogist combined their powers for the accumulation of innumerable facts, there was yet no theory perfect enough to account for the earth's formation, and to give the order of its successive stages.

And it was in this respect that geology became especially important to Lyell. He studied the different strata, the fossils, and the rocks that contained no fossils, earthquakes, volcanoes, the courses of rivers and glaciers, the fall of avalanches, and in fact all the phenomena connected with the changes going on in the earth, and it seemed to him that, as nature always works harmoniously and according to fixed laws, it might be possible to learn how all the changes that have taken place came to pass, and to formulate some law that should explain the workings of nature in this regard. Whle yet a student at Oxford a hint of the great system that he was to build up came to Lyell, but as this was in direct opposition to the popular theory of the history of the earth, he refrained from making it known until his studies and experience should have made him better able to pronounce upon such an important matter. With this in view he began to travel, visiting France, Germany, and Italy, and making the most accurate observations on everything that came in his way.

He studied the rocks of the Jura, the Alps, and the Valley of Chamouni, the glaciers of the Rhone, and the floods of the Valois, and in his descriptions of these places showed remarkable power both as a botanist and geologist.

When he returned from his journey he began geologizing through England, examining chalk beds, crystallized rocks, alluvial marsh lands, and clay pits, and from his indefatigable industry soon became known to all the leading geologists, who were glad to give to his powers of observation and generalization the tribute which they justly deserved.

In 1823 he was elected a secretary of the GeologicalSociety, being in his twenty—fourth year. In the same year he visited France again, and saw Cuvier and Humboldt, both of whom recognized in the young geologist a worthy student of science. For several years after this Lyell's time was spent, partly in England and partly on the Continent, studying and glacial action, and preparing his work on geology which appeared in 1830.

Up to this time there had been a wide diversity of opinion among geologists as to the causes of the changes in the earth's surface. About the middle of the seventeenth century, Steno, a Danish geologist, gave to the world his explanation of fossils, claiming that they were the mineralized remains of animals, and said that the animals now in existence could only be properly studied by comparing them with the fossil remains of other ages. This was a step far in advance of the time when it was claimed that the shells and fossils found in mountains remote from the sea were made by the stars, or produced by some trick of nature, and the suggestion to study the past from the present was made in the true scientific spirit.

A century later, Hutton, a Scottish geologist, whose love for the chemistry had led to the study of geology, made some interesting observations on the changes which water will produce on the hardest rocks, and gave it as his belief that all the former changes in the earth's surface were due to the same agents that are now at work. He claimed that the strata which composed the earth at present were once under the sea, and said that the ruins of an older world were visible in the present structure of our planet, and that the same forces were now at work destroying the hardest rocks and carrying them to the sea, where they become again altered by volcanic heat, and that thus there was a constant change going on all the time in which nothing was lost, but everything gradually transformed.

At that time the popular theory of the changes in the earth's surface was quite opposed to the views of Hutton; nearly all scientists taught that all the changes that had taken place in the earth's crust had been caused by great and sudden convulsions, such as earthquakes, volcanic eruptions, floods, upheavals and depressions of the land and similar phenomena, which clearly indicated that nature acted spasmodically, and the earth had reached its present condition through the action of forces very different from those now in operation.

This view would, of course, preclude the idea that nature acted in a uniform or constant way, and supposed all her laws to be subject to violent changes.

Hutton's theory was recieved with little favor by the public, who saw in it a disposition to ignore the Biblical account of the creation, and the author recieved a storm of abuse from critics who thought that any inquiry into the origin of the universe was an act of impiety. But to all his opposers Hutton only replied that the laws of nature were immutable, and that the forces which governed the changes on the earth were as unalterable as those which kept the planets in their courses, and held the reins of life and death.

Hutton's theory was far in advance of his age, and was not generally accepted even by the most liberal men of science, but it is interesting to know that it became Lyell's work to elaborate the same idea, and to so strengthen it with indubitable proofs as to make its acceptance a necessity.

Contemporarily with Hutton lived the geologist, William Smith, whose good fortune it was to carry geology a step farther than it had yet reached.

The different strata of layers found in rocks had heretofore attracted the attention of geologists very slightly, and the beds of different materials which lay one over the other in pits, and rock quarries were little regarded. Thery were known to exist, just as the beds, or strata of mud, gravel, and sand were known to alternate in the mouth of a river, but they were hardly recognized as of more importance than that given by the old botanists to the different colors of the rose, or the varied tints of the lily.

But Smith studied the strata of all the rocks that he saw, and was able, from his accurate observations and logical reasoning, to deduce a theory of the earth's formation in which the strata formed a prominent part.

Two important discoveries were made by this geologist : first, that there is a regular order of succession of the strata, or beds, which proves them to have been formed at different times, and that in every case the beds at the bottom are the oldest; also that this same order of succession may be found all over the world; and so sure was Smith of the truth of this theory that even at the time of its first conception he guessed correctly the nature of some hills he saw in a distance by their relative position in regard to certain rocks in the county through which he was passing. The second discovery was of equal importance, namely, that each stratum contained fossils differing from those fossils in other layers, and that knowing the fossils one could determine the strata from which they were taken. From these two discoveries Smith deduced a general law which he summed up as follows : The same strata are always found in the same order of succession, and contain the same peculiar fossils.

Lyell's "Principles of Geology," which was pupblished nine years before the death of Smith, incorporated the views of all those geologists who had striven to prove that nature works in a uniform manner, and the author announced as the foundation of his theory the belief that the past could only be studied from the present.

Lyell's studies, travels, experiments, and observations had all led him to the same conclusions, that in nature there is no life or death, but only change; and that the same agents which produced the great changes on the earth's crust are at work now, although they work so slowly that the effects are almost imperceptible.

Murchison, a distinguished contemporary of Lyell, taught that the mountains, and hill, and valleys had been created by great and violent convulsions of nature. This was called the convulsionist theory and had many adherents, who explained every change by saying it was the result of some great catastrophe.

But Lyell had the book of nature with a clearer eye, and his study had led him to a belief more in harmony with the known laws of the universe. He taught that those subtle alchemists, the rain, and the frost, and the snow, the rivers and the glaciers, carried on their silent work of transformation in the remote ages as surely and as steadily as they labor now; that the river which comes down from the mountain cutting its way slowly through the solid rock till the path has deepened into a trench, and the trench widened into a ravine, and the ravine become a valley, is but a type of the action of all the rivers that have flowed since time began; and that the rain and frost which splintered the mountain crest into peak and pinnacle, and carved out crag and cliff from its rocky sides are still carrying on the work begun when first the mountains were upheaved by the great forces working in the interior of the earth, and never to cease till all the ages of the future have passed away.

Lyell took the minerals and rocks of the earth and placed them one by one in their proper places till the great book of the earth's history could be read from beginning to end, and all its text and pictures rendered so clear that even the most ignorant could understand it, and know that the child who stands by the mountain rill watching the strong current sweep along the shining pebbles is reading the secret by which the great rocks were formed; and that the violet which drifts upon the surface of the meadow brook till it is caught and tangled among the debris at its outlet is but a type of those great deposits which it took thousands of years to harden into imperishable forms of beauty : while the tiny sea—shell which he picks up along the shore tells the same wonderful story of those bygone ages when all the teeming life of the animal and vegetable worlds had not yet turned to stone.

The fact that the different strata could be recognized by their fossils was made by Lyell the basis of the law of succession of life upon the globe, and from this time geologists began to speak of the different ages of the world in reference to the life of plants and animals upon it; those rocks in which few fossils are found belonging to one age, those which contain fossils resembling living species, another age, and so on, until the present was bound to the past with the strongest links, and the succession of life was proven with the same ease that one might demonstrate a law of mathematics.

Although the "Principles of Geology" met with severe criticism from those who fancied that they saw in it proof that the author wished to inculcate views different from those taught by the Church as to the origin of the world, it grew steadily in popular favor, and is the theory accepted at the present time. And Lyell's work later on showed the same spirit of progressive thought.

His travels in Europe and America only served to deepen his belief in his first impressions. Thirty years after the publication of the "Principles" he published his "Antiquity of Man," in which he claimed that the human race was many thousands of years older than had been supposed, a theory which later researches have all strengthened, while his observations on the great ice age an equal value for later geologists.