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The records of civilized nations can hardly point to a time when man had not yet learned to tame and bend to his will the beasts which seemed only created for his use. And the great value of these four-footed slaves soon became so apparent that the entire wealth of families and tribes was often counted by the number of oxen, camels, sheep, horses and elephants which were owned; these animals were also used as the medium of trade, and in agricultural countries, where the inhabitants had few and simple wants, it often happened that gold and silver money was quite unknown, and wheat and barley were exchanged for sheep and oxen, just as now the same products are brought to market and sold for so much coin.
The animal kingdom thus occupied a very important place, and the chief who could count his camels and horses by the hundred was the one who received the greatest honors, and could hold easy dominion over his less wealthy neighbors.
Very early, too, we find that men learned to put a different and greater value on animals than that granted by the mere power of possession, for in many countries they were worshipped as gods, and received divine honors; and even those which were not actually regarded as deities, were in many cases held sacred, from the great reverence which was paid to life.
Thus many animals not used for food, such as cats, dogs, crocodiles, and serpents, were looked upon as sacred to certain divinities, and it was considered an ominous sign to kill one of these, even by accident, while he who should so disregard custom as to be willfully guilty of the death of one was regarded with the greatest horror.
In Egypt this superstition arose largely from the popular belief that the soul of man after death entered the body of some animal as a punishment for the sins committed in life, and the study of medicine was hindered by the abhorrence attached to one who dared to aid his studies by the dissection of a dead animal; but in many cases, as in India to-day, the dislike to slay an animal, needlessly, arose from the awe and mystery which were attached to life, which the mystics of all European and Asiatic nations invested with the utmost sacredness.
For many centuries man was content to know that certain animals could be put to certain uses, and were called by certain names, and let his interest cease at that point.
But later, when Greek civilization and learning had combined to invest all knowledge with priceless value, the animal kingdom began to be looked upon as an interesting study, and Aristotle, whose genius left no branch of knowledge unimproved, may be said to have founded the science of zoölogy when he incorporated among his other works an account of all the animals known to the ancients, and made some attempt at classification and description.
In this work Aristotle sums up such a vast number of statements in regard to the resemblances and differences of animals, their anatomy and the functions of the various organs, that the modern naturalists have only had to follow the way he marked out to arrive at some of the most interesting discoveries in Zoology.
It is supposed that Aristotle was assisted in his zoölogical studies by the great number of strange animals that Alexander the Great had sent to him from Asia and Africa, for this monarch was justly proud of the genius of the famous philosopher, and took pleasure in affording him every opportunity for displaying it.
Aristotle placed the backboned animals first in his order of classification, and distinguished between these and the white-blooded animals, which have no backbone, and are divided into rings or segments.
Although the student who now reads the works of Aristotle will find many statements that are absurd and false, they do not detract from the genius of the man who first conceived the possibility of arranging the different families of the animal kingdom so that they might be intelligently studied, and it has been suggested by an eminent modern authority that the errors in Aristotle's treatise may have arisen from the fact that the students who listened to his lectures incorrectly reported his notes, and that it is these notes which form the greater part of what is now known as Aristotle's treatise on animals.
Hippocrates, who died ten years before the birth of Aristotle, had taught that the practice of medicine could not be properly followed without a knowledge of the structure of the human body, and his studies in zoölogy first led to the foundation of the art of healing upon scientific principles. Many of his descriptions of the symptoms and developments of fevers and other diseases are found accurate to-day, and although his theories have for the greater part fallen into disuse, he will ever be remembered as one of the world's most progressive thinkers, whose work it was to destroy the superstition that all disease resulted from the anger of some offended deity, and to found instead a belief based upon reason and experiment.
Aristotle's influence on thought was shown by the fact that when the great library of Alexandria was founded, there were gardens, menageries, and dissecting rooms especially devoted to the study of zoölogy; and if the results of that period of investigation had not been lost it is probably that many of the modern discoveries in zoölogy would be but the finding again of well-known truths.
After the decline of the Greeks the Arabs became prominent as cultivators of literature, the arts and science. Taking for their motto: "He dies not who gives his life to science," these careful students stored up the priceless treasures of Greek learning, and at time when the nations of Europe were sunk in ignorance and superstition, kept alive the spirit of scientific inquiry and preserved for posterity much of the wisdom of the ancient world.
About the middle of the sixteenth century the study of zoölogy received a fresh impetus from the works of Gesner, a Swiss physician and professor of Natural History at the University of Zurich.
Gesner published a valuable work on animals in which he received the old authorities, contributed many important facts in regard to living species, and gave illustrations of many fossils.
The link between the past and present was formed by the work of Gesner, for modern zoölogy dates from that time; and although nearly a century passed before the appearance of another eminent naturalist, yet the work went slowly on, and the interest in zoölogy kept steadily increasing, so that by the end of the seventeenth century it was possible to indicate a very decided advance in that study.
Harvey had discovered the circulation of the blood, and given the world the benefit of his wonderful anatomical discoveries which revolutionized the study of medicine; Ray had published his classification of the animal kingdom, the scientific merit of which has won him immortal renown; and the use of the microscope had led to the knowledge of those minute forms of animal life which had hitherto escaped observation, and to an acquaintance with the anatomy of insects.
Thus the beginning of the eighteenth century found the world in a state of expectancy in regard to the natural sciences, and the work of Réaumur, who was born early in the century, gave evidence that the time was fruitful in original thinkers.
Réaumur's labors were confined almost entirely to zoölogy, though his experiments in chemistry, wherein he discovered the art of tinning iron, and made several contributions toward the manufacture of iron and steel and porcelain, were of great service in the mechanic's arts.
His work in zoölogy consisted of a most exhaustive study of insects. He describes their habits and anatomy, and was the first zoölogist to bring their instincts into notice. The work was published in six volumes, and has been a valuable source of information to succeeding entomologists.
Linnæus' work on zoölogy was of great value, as his method of classification enabled students to easily place any animal in its proper order and family, and Buffon, another zoölogist of the eighteenth century, gave to the world a popular illustrated work on the animal kingdom which will ever be remembered as being the inspiration of more than one eminent naturalist.
Buffon's work was not distinguished for the careful exactness which belongs to other writers, but his glowing descriptions, and animated style gave his volumes a peculiar value. Zoölogy from that time ceased to be regarded as the province of the learned, for Buffon had shown that it could be a source of amusement and instruction to the most unscientific; and we have only to call up the picture of Linnæus and Cuvier sitting in a college library and poring over the fascinating pages of this author to realize the important influence exercised by Buffon in the history of zoölogy.
Still another zoölogist of the eighteenth century was a Lamarck, a French author, who, although he did not begin the study of zoölogy until after he was fifty years old, is regarded as one of the greatest authorities by the student of to-day.
Lamarck's principal work was devoted to the study of intervertebrates, or animals which have no backbone, and he raised this branch of zoölogy to a very important place. He was the first master to insist upon a thorough acquaintance with the lower forms of life as a preliminary study to the higher forms, and so minute and exact were his studies of the lower animals that his works have become the text-books for all time.
Lamarck was among the few zoölogists who taught that the lower animals were first formed, and that the vertebrates or back-boned animals are of much later origin, a view that has been confirmed by the discoveries in zoölogy, and by the greatest modern naturalists.
And thus the study of zoölogy was led on step by step, one naturalist making a discovery and another using it as a basis for a new ground-work of belief, until the nineteenth century found the scientific world possessed of a tolerably clear idea of the resources of the animal kingdom, and its history from the earliest times. And then the story was taken up again by others interested in the great wonder-book of nature, and thus we find that time cannot interrupt, but only make more complete, the work of those who give their lives to science. Among the worthy successors of Linnæus, Lamarck, and Cuvier may be counted Louis Agassiz, whose name is familiar wherever the student of science is found.
Agassiz was born at Motier, in Switzerland, in 1807, exactly one hundred years after the birth of Linnæus, and his early life very closely resembled that of the illustrious child of the North. Like Linnæus, his childhood was passed in a quiet country parsonage, situated on the borders of a lake, and embracing a view of a region of such picturesque beauty, that it could not fail to impress itself upon the mind of the child.
The home-life of the parsonage was very simple, and the children of the family were early taught to regard only those things as valuable which were independent of wealth, and their childish pleasures were all such as could be found in any of the unpretentious little homes that surrounded them.
Unlike many of the great naturalists who only took up their special work late in life, Agassiz may be said to have begun his life-work in his early childhood, though he himself was unconscious of it.
For, like Linnæus and Cuvier, his first impressions of nature were received form the games and employments of his country home; and in his boyish taste for collecting nests, eggs, birds, and other pet animals, and in the little aquarium, supplied with specimens from the lake, could be traced the small beginnings of his scientific career.
Thus the love of nature, and the finding out of her secrets, began with the boy's first consciousness, and in all his out-of-door sports he was laying up stores of valuable information. To him, as to all country children, the different seasons of the year brought each its offering of gifts and laid them at his feet; and from the first spring blossom to the fall of the snow all nature seemed a harmonious whole, and the wide earth but a treasure-house where one might gather largess at his will. And as the years passed, Agassiz learned more and more of the great forces which linked him with the world of nature around him, and began to understand the sympathy which the genuine naturalist feels for all forms of life.
Besides these lessons, learned in the fields and woods and by the shores of the lake, where nature herself was the teacher, Agassiz had a few simple tasks out of books, his father and mother being his teachers, and, up to his tenth year, he received no instruction outside of his home.
But a boy so intelligent and observing as Agassiz could not fail to learn many things not included in his daily hours of study, and the home-life of Motier, which was in many respects very primitive, furnished the boy many a self-imposed but not the less instructive task.
From the shoemaker who came twice a year to fit the family out with boots and shoes, the boy learned how to make a tiny pair of shoes for his sister's dolls, from the tailor, who was a guest in the house while making the spring and winter outfits, he learned to fashion a suit of clothes, and when the cooper arrived to put the barrels and hogsheads in order for the vintage, he found an apt pupil in the boy to whom nothing seemed uninteresting, and who gained, in these childish amusements, much of that training of the eye and hand which were invaluable to him later on when dexterity and delicacy of touch were so necessary to his scientific pursuits.
And the times of seed-sowing and harvest and vintage, when all the members of the family took an unusual interest in the farming affairs, were also made to contribute their share toward the education of the future naturalist, who learned many practical, useful lessons about growing plants at a time when the learning seemed only childish pastime.
The vintage was the great annual holiday season, when almost the entire population gave themselves up to the business of gathering the grapes and making the wine, and the merry-making attendant upon such a festival. Here all ages and classes met together, the very old and the very young being alike able to give their share of work and fun, and it was amid such scenes that Agassiz early learned to sympathize with the tastes and interests of everyday-life, and imbibed that generous love for humanity which was such a distinguishing trait of his character.
When he was ten years old Agassiz left home to attend school at Bienne, twenty miles away, where he remained five years, coming home only for the vacations.
They were years full of pleasure to the boy, who developed a great taste for study, and made a lasting impression upon his mind; for long before their close he had learned the great lesson for all scientists, to love knowledge for its own sake, and not merely as the means to an end.
During this time his taste for natural history was confirmed, and the little collections he had made at Motier gave place to others more in keeping with his ambitions. He did not have the benefit of a teacher in these pursuits, and the pages of manuscript filled with notes were written on a plan entirely his own. He made at first no attempt at classification, being content to give all the plants and animals for which he knew Latin names, with the design of extending the list gradually until it should include the entire animal and vegetable kingdoms.
Although this design may seem childish enough, it yet shows the birth of the true scientific spirit, which begins with inquiry into the familiar, and never ceases until the unknown has been explored as widely as possible.
And although Agassiz's attempts at studying natural history were at this time so desultory, and included only general observations on the appearance and habits of the specimens, they yet were fruitful in laying the foundations for those accurate studies from nature which distinguished the work of this naturalist.
Meadow, field, forest, and stream were haunted by the boy, who thought no living thing uninteresting, and his room was gradually turned into a small museum of natural history. Birds, insects, and fishes were collected with great care, and their modes of life so carefully studied that the knowledge thus gained became a storehouse of useful facts when Agassiz became interested in the graver problems of natural history. He raised caterpillars form the eggs and studied with minute care the different kinds, describing their habits and differences of diet, and the length of time passed in the chrysalis state, and accurately noting the characteristics of the great variety of butterflies and moths, with which he soon became familiar.
The songs of the birds, their twitterings, scolding, changes of position, habits, and instincts were all as well understood by the boy-naturalist as the voices of his friends; and in his autobiography he says that what he knew of the habits of the fresh-water fishes of Central Europe was almost entirely learned at that time, it being a matter of great surprise to him when he became acquainted with the works of the principal authorities on fishes, to find how little they knew of their habits and life, things which Agassiz himself had been familiar with since boyhood.
The parents of Agassiz had intended that he should leave school at fifteen, and enter commercial life, for they had never associated any serious meaning with the boy's love for natural history, and the years passed at Bienne seemed a sufficient preparation for a life to be spent at the desk of a man of business. But Agassiz's love for study had grown to such proportions by the time it became necessary for him to leave Bienne that he begged for two years more of student life, and although this called for some self-denial on the part of the parents, who had only a limited income to depend upon, the wish was cheerfully granted, and the boy was allowed to enter the college of Lausanne.
And this step, whose importance no one then conjectured, was in reality the turning-point of the boy's life. Here he heard his first lectures on zoölogy, based upon the teachings of Cuvier and Lamarck, and learned the great importance of system and classifications, and that the greatest authorities could differ in regard to the name and place of the various classes. The view of Cuvier in the "Règne Animal," and of Lamarck in his work on the invertebrate animals, all showed conclusively the importance of anatomy in the study of zoölogy, as their conclusions were drawn chiefly from observations on the structure of the animals, and depended little on other points. Agassiz was thus led to see the great value of anatomy, and his interest in this subject was at once awakened.
Lausanne possessed the only collection of animals in that part of the country, and Agassiz's newly awakened interest was stimulated by the sight of so many specimens hitherto unknown to him; he visited the museum as often as possible, observing and comparing the different varieties with his usual intelligence, and, no longer content with this superficial way of study, ardently began to long to understand the internal structure, so that he might be led to the scientific way of classification.
In this respect he was fortunate in having an uncle at Lausanne, who was a physician, and who lent a willing ear to Agassiz's intelligent questioning. And it was through the influence of this relative that all thoughts of a commercial life for Agassiz were finally abandoned, and he was allowed, when seventeen years of age, to enter the university of Zurich as a student of medicine.
Here Agassiz's real scientific training began, as, for the first time, he came under the instruction of men who were studying nature from her own book, and did not depend utterly on the teachings of others; and this originality was of the greatest benefit to Agassiz at this time.
He entered upon his medical studies with the greatest zest, being delighted with the idea of taking a profession so closely allied to his favorite pursuit of natural history, and as his teachers lent their aid and encouragement, whenever it was possible, his life at Zurich promised to partake more of the nature of a holiday than of a serious working time. His anatomical studies were especially interesting, as in that department he felt that he was not only fitting himself for his work as a physician, but that he was put in the way of following out the suggestions contained in the works of Cuvier and Lamarck, and entering upon a wider field of scientific inquiry than he had been before able to work in.
The first lectures he heard in anatomy roused such an interest that he could think of nothing else, and in speaking of this time afterward he said that he could see nothing but skeletons, and could find no pleasure out of the dissecting-room. With his customary zeal he at once began to make a collection of bones and skulls, dissecting all the animals he could find, and, as was the case at Bienne, turning his rooms into a small menagerie.
A large pine-tree in the corner of the room became the home of scores of birds which flew about the head of the young naturalist while he was busy arranging his collections, and the streams and lakes furnished specimens for a new aquarium, while shells, minerals, and living pets of all kinds, showed that Agassiz had in nowise changed his tastes from those which distinguished him as a child.
A private library at Zurich, to which Agassiz had access, held some valuable works on natural history, and here the young student spent many an hour copying the text and illustrations in his note-books, as he could not afford to buy the necessary text-books. Two volumes of Lamarck's "Invertebrate Animals" were copied at this time, and although this plan of study might appear unnecessarily hard, yet it after all served a good purpose, as it made Agassiz depend less on text-books and more on observation and original research, a thing which could not fail to have a beneficial effect on one who was destined to become distinguished as an independent thinker.
During his two years' stay at Zurich, Agassiz was diligent in his application to the study of medicine, but the love of natural history was gaining greater sway over him year by year, and the books and reports of those naturalists who had enjoyed foreign travel took such hold of his fancy that he, too, became possessed of an ardent desire to travel and study the wonders of nature for himself.
It is not surprising, therefore, that at the end of two years, he persuaded himself and his friends that it was absolutely necessary for him to enter the University of Heidelberg for the purpose of pursuing his medical studies to the best advantage, for there he knew he should find some of the most distinguished naturalists of Europe.
The life at Heidelberg was but a continuation of that passed at Zurich, with the exception that soon after his arrival at his new quarters Agassiz made the acquaintance of a young man who was, like himself, very deeply interested in natural history, and who became his intimate friend almost from the first moment of meeting.
The two friends were together constantly, and studied zoölogy in the fields, woods, streams, fish-markets and museums, each benefiting the other by his experience and advice; for although Agassiz had by this time become familiar with a large part of the animal kingdom his friend Braun was the better botanist of the two, and thus they were able to derive mutual benefits from each other's company. When not abroad botanizing and zoölogizing they spent much of the time in their rooms, where, while one prepared specimens, arranged collections, or dissected cats, dogs, fishes, and butterflies, the other read aloud from some work on anatomy or physiology. His intercourse with Braun proved of the greatest service to Agassiz, who, from that time, ceased to regard the study of living animals as of paramount importance, and began to take a wider view of the aims and ambitions of the naturalist.
The work of Cuvier, and other specialists on fossils, also attracted his attention about this time, and in fact the experience of Agassiz at Heidelberg serviced to so deepen his perception of his own peculiar powers as to make him dream more and more of becoming a naturalist to the exclusion of everything else.
After a year and a half spent at Heidelberg Braun determined to enter the university of Munich, and Agassiz accompanied him. Munich was rich in the presence of several teachers and travelers of distinction, and Agassiz at once felt the inspiration of the new influence. His medical studies grew irksome to him, and his studies in natural history occupied nearly his entire attention, while his visits to the rooms of two of his new friends who had traveled in Brazil, and brought home a fine collection of fishes, awoke anew that love of travel which is the ever-present impulse of the true naturalist.
But travel was impossible at this time, and Agassiz was somewhat comforted for the deprivation, by a proposition from one of his traveled friends to describe the fishes brought back from Brazil. This was work of a character highly suited to the wishes of the young student, and he set about it with enthusiasm, keeping it a secret from his parents as he wished to surprise them with an evidence that his taste for natural history and distaste for Medicine might, after all, lead to some practical end.
Agassiz worked on the Brazilian fishes with an earnestness that well repaid the trust reposed in him, and the first volume appeared in the autumn of 1828, when the editor was in his twenty-second year. The work was well received by all European naturalists, who felt that it furnished a necessary link in ichthyological history, and Agassiz received from Cuvier a letter of warm appreciation of its merits, and the promise to incorporate it into his new edition of the "Règne Animal."
This success so encouraged him that he decided to undertake another work somewhat similar in character, and he therefore began his work on the fishes of Switzerland and Germany.
During his preparation of the "Brazilian Fishes," Agassiz was buoyed up by the hope that he might be included in the list of those who were about to start on scientific tours, hoping either to join Humboldt's expedition to Asia, or a similar excursion to South America under the direction of another naturalist.
He therefore undertook a regular course of training as a preparation for the journey, learning blacksmithing, carpentering, practicing sword and sabre exercises, and taking long walks day after day, loaded down with bags of plants and minerals. This course, he thought, would fit him to endure the disadvantages of travel through uncivilized countries, and it was a bitter disappointment to him to find that he could obtain no place as assistant to any one contemplating foreign travel.
However, he still kept on the path he had marked out for himself, and as a fine opportunity presented itself for studying the collection of fossil fishes in the museum of Munich, he at once undertook the preparation of a work on that subject. It was a fine chance for the young naturalist to show what he could do, as fossil fishes had up to that time received little attention, and it was Agassiz's own originality and vigor of thought that suggested the choice of this topic.
He employed two artists to help him in the work which progressed rapidly in spite of the fact that the author was at the same time engaged on his Fresh-Water Fishes of Central Europe, and hard at work studying for his diploma.
In the spring of 1830, Agassiz received the degree of Doctor of Medicine, being in his twenty-third year, and at the end of the same year left Munich for Switzerland, where he remained for a year working on the fossil fishes and fresh-water fishes, and practicing medicine as often as opportunity offered. But he was restless for the larger life to be found in the scientific circles of a great city, and in the autumn of 1831 started for Paris, though not without a certain dread of the future, as his financial prospects were anything but cheering.
But his scientific life in his new home was so inspiring that it repaid all the loss he suffered in personal deprivations. Humboldt and Cuvier received him with the greatest kindness, and the museum at Paris offered inexhaustible resources in the prosecution of his work on the fossil fishes. In this work Agassiz's aim was to determine to what geological period the different specimens belonged, and to trace the connection between the fishes of the past ages and those of the present time.
This was not an easy task, as in many cases it was impossible to obtain enough of the skeleton to distinguish the specimen without great difficulty. But Agassiz was undeterred by this circumstance. A tooth, a scale, or a spine served him as a guide into this wide field of research, and from these trifles his patient energy would reconstruct the entire skeleton, and bring back to life again, as it were, the dead animal which the long centuries had carve din stone. The importance of this work, which would service the twofold purpose of explaining the development of the different classes of fishes, and the succession of the layers of rock, as told by their presence or absence, was well understood by Agassiz, and it was a matter of great seriousness to him that his limited means should stand in the way of carrying on his studies to the best advantage.
During the year he spent in Paris he received a generous loan from Humboldt, whose high appreciation of Agassiz's talent never diminished, but Agassiz felt more and more the impossibility of depending upon chance for a livelihood, and in 1832 accepted a professorship at Neuchatel. His work on fossil fishes occupied him ten years, during which time he visited England, Germany, and France, for the purpose of studying the fossils in the various museums.
The publication of the first volume in 1833 at once placed Agassiz among the greatest living naturalists, and was received with the most distinguished favor by all the scientific societies of Europe.
In this work Agassiz made the very important discovery that the natural succession of the different classes of fishes, as regarded their development, also corresponded with the succession of the geological epochs, as marked out by the recent studies in geology.
While this work was in progress Agassiz also made some very interesting studies on the nature of the action of glaciers. Up to this time the theory about those great fields of moving ice had been based upon the convulsionist theories of the older geologists, and the presence of vast ice fields, and great boulders, in places where there seemed no apparent reason for their existence, was explained by supposing that nature worked by fits and starts, and that there could be no other way of accounting for her actions.
But from the year 1836 to 1846 Agassiz visited all the glaciers of Europe, and studied them with the greatest care. In these excursions he was accompanied by other men of science, who gave him help in special ways, and he was thus able to make the most thorough study of glacial action. One member made a microscopic study of the red snow, and the animal life it contained, another studied the flowers, another the temperature of the interior of the glaciers, and another the deposits or débris left by this slow movement.
The geologists of all countries had long been puzzled over the presence of boulders, fossils, and the quantity of loose unstratified material called drift, which were scattered over various places, where their appearance did not correspond with the geological formation of the rocks, and Agassiz's bold theory of glacial action, which explained these phenomena on simple and reasonable grounds, was received with unmistakable satisfaction and admiration.
Agassiz laid aside the theory of sudden convulsions of nature, and claimed that the glacial phenomena could be explained upon principles more in harmony with the ordinary workings of nature; and his ten years' study of glaciers only confirmed a conclusion to which he had been led early in his investigations.
According to this theory, the whole of the northern continent was once covered with ice which extended from the North Pole to the boundaries of Central Europe and Asia. Before this ice period the whole of that region had been covered with a luxuriant vegetation and was inhabited by the great animals which are now found only in the torrid zone. Elephants, hippopotami, and enormous flesh-eating animals wandered through the vast forests, and the rivers which flowed into the Arctic Ocean were the haunts of fishes and waterfowl, now only to be found in the streams of the tropics.
This condition of things existed for long ages, during which the earth was covered with verdure from the equator to the uttermost north, and the teeming life of the tropics extended to the polar regions. Then, by degrees, the whole aspect of nature changed, and from some unknown source, cold succeeded heat, and death came to take the place of life. Lakes, seas, and rivers were frozen, and the myriad living creatures they contained were changed to inanimate forms; over the vast plains stretched a great mantle of ice, which touched the flowers, shrubs, and trees, as if by magic, and turned them to stone, while the huge beasts, wandering through the forests, or basking in the sunlight of the northern shores, were overtaken by the same dreadful fate, which spread a shroud over the living face of nature and turned a scene of beauty to ruin and desolation.
Ages after this catastrophe, the sun's beams melted the ice and snow, which slowly began their retreat toward the north, and the ice-fields and glaciers of Central Europe along remain to remind the student of nature that the story they tell was a living reality, and not the fanciful imagining of the poet or romancer.
The acceptance of this theory accounted for the presence in the Siberian rivers of those remains of gigantic animals whose counterparts are now to be found only in the tropics, and explained the appearance of fossils, boulders, and other deposits in places where their presence had been hitherto unexplainable. And although it was elaborated during the years when Agassiz was busy upon zoölogical studies of the gravest importance, it lacked nothing of that conciseness, vigor, and attention to detail which distinguished all the work of this master, who considered every part of creation of equal interest and found zoölogy and geology alike but the means of reading more clearly the great design of the universe.
In 1846 Agassiz came to the United States on a visit, having for its object the pursuit of his scientific studies. At this time, when his face was world-wide, his theories were nowhere received with greater enthusiasm than in America, and it was a matter for no surprise that two years after his landing in the New World he was offered the chair of Natural History in Harvard University.
From that time his scientific work was confined to the continent and islands of America, and his many journeys, having for their object the study of zoölogy and geology, were all made in the interests of science in connection with those studies in the New World.
Agassiz's most important contribution to science after his settlement in America was his report upon the Florida Reefs, a strip of rocks fringing the southern coast of Florida, which had long puzzled the American naturalists, who had so far been unable to agree as to their geological formation. The Coast Survey of the United States was particularly anxious to have the question of their formation settled, both from a practical point of view in regard to navigation, and for scientific reasons, and Agassiz was asked to make an exploration of that region in the interests of the Government.
Agassiz accepted the commission with great eagerness, and made an exhaustive study of the reefs, arriving at the conclusion that these fringes of rocks, which were separated by deep channels, were not a freak of nature, but that the whole peninsula of Florida had been formed by successive circles of these coral reefs, the everglades being only filled up channels, and that the soft soil, now so shifting and uncertain, would in time present the firm appearance indicated by the older portions.
The report was valuable to the Coast Survey, as it determined the nature of the soil, and indicated what localities might be available as offering stable foundations for light-houses, signal stations, and the like.
The life of Agassiz from the time of his coming to America was one of ceaseless activity, and his lectures at Cambridge and in Charleston, S. C., where he resided for some time, formed only a small part of his work. His contributions to science were of the greatest value, and during the first fifteen years of his residence in the United States his essays on the geographical and geological distributions of animals; on the natural history of the United States; on the glacial phenomena of Maine, and kindred subjects, served to advance in a marked degree the sciences of geology and zoölogy, which were still in a process of formation, while the establishment of several scientific schools, which have since attained to eminence, were likewise attributable to the same master-mind.
In 1865 Agassiz made a journey to Brazil, having the twofold object of obtaining a needed rest from his usual work, and of making collections for the Museum of Natural History; and this expedition was fruitful in scientific interest.
He remained in Brazil something over a year, and was able to make a most satisfactory collection of Brazilian fishes, bringing away with him two thousand specimens obtained from the Amazon and its tributary streams and lakes. It was also a great source of pleasure to Agassiz to find, in the Brazilian tropics, evidences of the great ice-period, which proved to him that the glaciers had once covered that region, where now the rays of the sun are so powerful as to endanger life.
In 1871 Agassiz started out on another expedition, having for its object the study of the animals of the sea, for which purpose it was proposed to dredge the coast-waters down the Atlantic and up the Pacific as far as San Francisco. This work was especially attractive to Agassiz, as he believed that the study of the deep-sea animals would reveal many of the missing links between the fossil world and living species; and, beside this, he also expected to find evidences that the glacial phenomena, familiar to the northern hemisphere, were also to be found in the southern, and thus add a stronger proof that his glacial theory was correct.
The active work of the expedition began as soon as the Gulf Stream was reached, with the study of the Sargassum, or fields of drifting seaweed, which abound in those regions, and which was filled with minute forms of life. Agassiz was able to make a very satisfactory study of the Sargassum, and this good beginning was followed up by dredgings in the Barbadoes, which revealed some living sponges, so much like the fossils he had previously studied that Agassiz felt that his theories of deep-sea dredging were already bringing him a golden harvest.
On the coast of Montevideo Agassiz found strong evidences of glacial action, and on the coast of the Argentine Republic many interesting fossils were obtained from the huge boulders which were scattered everywhere; while the geological formation of the coast of the Straits of Magellan gave still further evidence of the truth of his favorite theory in regard to glaciers. Here he found a moraine composed of boulders, pebbles, and gravel, polished and grooved, and bearing all the signs of glacial action, while the ice- and snow-fields glittering upon the slopes of the mountains could only remind him of the glaciers of the Alps, thus proving to Agassiz that the ice period had extended over the southern as well as the northern continents, coming in both cases from the poles and retreating eventually in the same directions. Agassiz studied the glacier regions of the south for several weeks, and then the vessel proceeded on her way to new fields of investigation.
A trip was made to the Galapagos Islands, interesting to naturalists because of their recent origin and their peculiar varieties of plants and animals, some of which are different from any known in other parts of the world; and here Agassiz made some important studies on the formation of volcanic islands, of which this group formed an instance.
The voyage was then continued up the Pacific, the original plan to proceed to San Francisco being carried out by their reaching that city in August, 1872, having accomplished very nearly all that they set out to do. This was Agassiz's last scientific excursion; and, after his return to Cambridge, he busied himself with plans for a School of Natural History to be established somewhere on the coast of Massachusetts, and which was to be in operation in the summer, for the benefit of pupils and teachers from all over the country; an important plan, as it has resulted in the founding of various summer schools which have greatly advanced the study of science.
Lectures, essays, and study filled up another year, and in December, 1873, the work of the great student came to a close, and he passed away from earth leaving behind him the fruits of a well-spent life in which selfish aims and enjoyments had no share, and which was of inestimable value to science.