Popular Science Monthly/Volume 3/August 1873/Footprints in the Rocks
|FOOTPRINTS IN THE ROCKS.|
By CHARLES H. HITCHCOCK, A. M.,
PROFESSOR OF GEOLOGY IN DARTMOUTH COLLEGE.
SEVENTY years ago, a student belonging to Williams College, while holding the plough in his father's field at South Hadley, Massachusetts, turned over a flat slab of sandstone about three feet long. His attention was directed to what seemed to be a row of bird-tracks upon its surface. He had often noticed—as has every intelligent person—the impressions made by the feet of animals in the mud, upon the shores of rivers, lakes, and in the highway. But he had never before seen the imprint of an animal's foot upon the solid rock, and had been taught to believe that the ledges were suddenly called into being by the Almighty without passing through a tedious formative process. Here, however, was a phenomenon not to be explained in accordance with the popular opinion—real footprints in the solid rock—and how came they there?
It was before the days of much geological knowledge, but Pliny Moody exercised a common-sense method of explaining what he saw; for he concluded that these markings were made by some animal in an early period of the earth's history. Nothing was more natural to him than to surmise that they were made during the earliest aqueous deposit of which he had heard—the muddy sediments left by the Noachian Deluge. Hence he pointed out these foot-marks to his friends—the specimen being utilized for a stepping-stone at his front-door as having been made by Noah's raven when wandering in search of dry land. The slab is still preserved, and the impressions appear to have been made by one of that remarkable group of animals which abounded in New England during the Triassic or New Red Sandstone period.
Thirty-five years later, as Mr. W. W. Draper, of Greenfield, a village thirty miles farther north, was returning home from church, his attention was arrested by the sliding of snow from some large paving-stones leaning against a fence. As he turned his eyes, he saw a row of apparent ornithic impressions on the slab, shown very distinctly on account of the reflection of the sun's rays from a wet surface. A philosophic induction was the result of his observation, and he immediately remarked to his wife: "There are some turkey's tracks made three thousand years ago!"
These two minds, though untutored in scientific lore, each independently of the other, expressed that fundamental generalization of paleontology which has never been set aside, though wondrously amplified and illustrated since that time: that these impressions were made by living animals in immensely remote periods, when the physical geography of the country differed from what it is at present—that is to say, when the existing solid ledges were in the formative process.
Mr. Draper soon communicated his views to his friends, especially to Captain John Wilson. Captain Wilson did the same to Dexter Marsh, and Mr. Marsh to the village physician, Dr. James Deane. All these gentlemen coincided with the theory of Mr. Draper, that the markings were turkey-tracks; but, as none of them were geologists, they felt the need of competent advice. Accordingly, Dr. Deane sent descriptions of the slabs to the State Geologist, the late Prof. Edward Hitchcock, of Amherst, urging him to come and examine them. A similar sketch was sent to the late Prof. Benjamin Silliman, of New Haven, who expressed no opinion about it, but wished Prof. Hitchcock to investigate the subject. As soon as it was convenient, this gentleman went to Greenfield and examined the specimens. His acquaintance with geological literature and methods of investigation apprised him that this new theory, though plausible, must pass through a severe ordeal before it could be established. Not merely was it questionable whether footprints could be preserved for ages, but it was a monstrous assumption—unheard of in geological circles—to talk of birds as a part of the Triassic fauna! Such an announcement could not fail to evolve unanimous disapproval; and, if premature, if published without careful investigation, it might prove to be an egregious blunder, and haunt the unfortunate author through his lifetime.
The scientific investigation of the subject having been thus urgently placed in Prof. Hitchcock's hands by those immediately and remotely interested, he spent the summer of 1835 in studying the characters derived from the progression of animals, whether birds or quadrupeds. Visits were made to all the sandstone-quarries in the Connecticut Valley, to menageries, museums, and libraries, thus insuring the inspection of all slabs exhibiting similar impressions, an examination of the feet of living animals, especially of those most nearly allied to the new forms, and the assurance that nothing similar had ever been found in any part of the world. The result of this protracted investigation indicated the truth of the first surmises—that these impressions were actually made by the feet of birds in the Triassic period. A full account of the discoveries was published in Prof. Silliman's magazine, the American Journal of Science and Art for January, 1836. Descriptions were given of seven species of avian impressious, called Omithichnites, or bird-tracks on stone. One of them was a foot of gigantic dimensions, not less than sixteen inches long, three times larger than its nearest living representative. It was no wonder that, in these early days, even the father of the science hesitated to admit these monsters into his ichnitic family, yet so exact are the laws of comparative anatomy, and so like the rows of impressions made by living feet were these giants, that a relationship to existing groups could be no longer denied.
A few geologists accepted these doctrines immediately after their promulgation; but most of them, as well as the community in general, doubted whether the preservation of foot-marks were possible, and especially whether they could have been made by birds. Some thought the resemblance was fanciful; others that they were the remains of peculiar marine plants. The public mind, which had no scientific appreciation of the subject, saw abundant opportunity for witticism, and did not spare the shaft of ridicule. The American Association of Geologists and Naturalists at length appointed a committee to investigate the subject, including in the list both the friends and opponents of the new views. They visited Prof. Hitchcock in due time, explored the quarries, examined his specimens, and became convinced unanimously that his views were correct. Their report to the Association states that "the evidence entirely favors the views of Prof. Hitchcock, and they regret that a difference had existed, if they did not feel assured it would lead to greater stability of opinion." This committee consisted of H. D. Rogers, E. Emmons, Lardner Vanuxem, Richard C. Taylor, and T. A. Conrad.
The public generally acquiesced in the truth of this report; they ceased to ridicule, and began to believe that a new chapter in the earth's history had been laid bare for perusal; great popular interest was excited in the foot-marks, and at the present day everybody has heard of the wonderful tracks upon stone in the Connecticut River Valley. The name of their principal expounder, who first published an account of them to the world, and waged a seven years' contest with his compeers and the public on this account, has become indelibly associated with them.
The results of Prof. Hitchcock's researches have been published in two large quarto volumes entitled "The Ichnology of New England." Of other publications, the "Ichnographs" of the Connecticut sandstone are worthy of notice as a monument to the memory of Dr. James Deane, whose early interest in the foot-marks never flagged, and who applied himself earnestly to the study of geology, so that his later writings have become invested with the authority of an able and accurate observer.
Amherst College now possesses the unrivalled collection of ichnites collected by Prof. Hitchcock. They occupy a room 100 feet long and 40 feet wide, and are more than 20,000 in number.
The first scientific publication concerning fossil foot-marks is contained in the Transactions of the Royal Society of Edinburgh in 1828. Six years later, Prof. Kaup described the tracks of the Cheirotherium, a beast with hands, upon Triassic sandstones in Germany. The animal must have equalled an ox in size, with hind-feet shaped like the human hand, which were about three times larger than the front-feet. He is generally supposed to have been a batrachian. The earliest description of the American ichnites appeared in 1836.
The Triassic formations on the Atlantic slope are disposed in long and narrow areas. These may correspond with the spaces occupied by estuaries before the deposition of the strata. We may suppose that an arm of the sea extended northerly from Long Island Sound to New Hampshire along the Connecticut Valley, possibly connecting, beneath the Sound and North River, with a similar estuary running southerly to Virginia. If we transport ourselves in imagination to these ancient shores, we shall see that the animals left their hiding-places and were traversing the soft mud laid bare by the ebbing tide, in search of food. The heat of a tropical sun quickly hardens the mud, so that the returning tide, in bringing a fresh deposit of mud, does not wash away the impressions already made on the lower layer, but carefully covers them over. The imprints have, therefore, become a species of mould into which another muddy fluid is poured, and by hardening is made to copy the foot-mark like a plaster cast. Hence, when artificially cleared, no matter how many ages subsequently, the strata will present to view the depressed print below and the cast of the foot above, both as perfect as the respective fineness of the mud and its degree of rapid induration by the sun will permit. This process of deposition may have been repeated, just as it may now be studied, in the Bay of Fundy, till the whole estuary was filled up, partly with fine mud and clay, partly with beds of sand and gravel, all more or less marked by the feet of animals, interspersed with volcanic beds of lava, tufa, and conglomerate, and rare chemical deposits of carbonate of lime, salt, and gypsum.
The Ichnozoa, or the animals who made the tracks on stones in Triassic times, may be referred to several prominent divisions of the animal kingdom. The first, and highest in the scale, is a group of five species, remotely allied to marsupials, which, from their osseous remains found in Europe, we know must have flourished in that period. The most characteristic is a five-toed quadruped, about the size of a lion, whose foot is not unlike that of a carnivorous animal. The others had unequal feet, larger behind and smaller in front. The most important groups are those referred to birds, embracing thirty-four species; equally divided between those related to the ostrich family—thick-toed—and those with long, slender toes, like the crane and heron. These are the impressions chiefly relied upon to prove the ornithic character of any of the Ichnozoa, as they show distinctly the phalangeal joints of the toes, like the tracks of the ostrich, turkey, and our common domestic fowls. The feet are invariably trifid, and the number of phalanges corresponds perfectly to that observed in the toes of all living birds, viz., three in the inner, four in the middle, and five in the outer toe, including the claws. The inner phalanges are united to the lower leg-bone abreast of each other, a little back of the middle one, and thus the imprint may also show rounded impressions made by the heel, which have been mistaken for phalangeal markings. This thick-toed group invariably took very long steps, corresponding well with the ordinary gait of their living representatives. One of them, with a foot less than three inches long, had a stride of 25 inches, showing a general structure like that of the waders. Moreover, the entire width of the track-way is scarcely greater than that of each individual foot, indicating a very narrow body, stilted high upon long legs. The smallest of this group may be compared with the living snipe; the largest, having a foot 18 inches long, must have equalled in size the largest of the recently-extinct birds of New Zealand, the Deinomis giganteus, 10 feet high. The principal genus is the Brontozoum (the animal giant); and of the thousands of examples of those yet exhumed, not one shows any features in addition to those described, neither a fourth toe, the trace of a front-foot, nor any indication of a tail. Hence, though suggestions as to their reptilian character are abundant, we shall wait for proof that some distinct reptilian feature is joined to the ornithic, before allowing that the Brontozoum, or Grallator, were not true birds.
But the next group gives evidences, neither scanty nor ambiguous, to prove the existence of a large number of "ornithic reptiles," or "reptilian birds." This order is now entirely extinct, and was first made known to the world by E. Hitchcock's description of the "ornithoid lizards, or batrachians." He saw that some of the characters were ornithic, and that others were reptilian, so that he was compelled, though reluctantly, to refer them to an altogether new group of life. Since this reference, an abundance of discoveries has confirmed these views; and the name of Herpetoids has been suggested for them by Prof. Dana.
The general form of the animal was kangaroo-like, with enormous hind-limbs, a prominent tail, and small front extremities, which were rarely if ever brought to the ground so as to make an impression. The animal may often have walked only upon the trifid hind-feet, showing neither the front-feet, the long shin-bones, nor the caudal appendage. We have seen such rows of trifid impressions, 25 or 30 in number, which might hastily be referred to the feet of birds. But, though the general appearance is ornithic, and the number of phalanges agrees with those of birds, the thirty-first impression reveals a kangaroo-form on all-fours—two small five-toed feet in front, two trifid impressions of larger dimensions at the end of a long heel-mark behind, followed by a heart-shaped print, or a trail, that has come from the caudal appendage. This remarkable quadrupedal display is succeeded by another row of trifid impressions; just as if the animal stopped to rest on his journey, and then resumed his line of march.
Surely no one can doubt the quadrupedal character of this Anomœpus. Yet, it was not till after years of discussion and discovery had
elapsed that his true relationship was appreciated. The first-discovered rows were supposed to be ornithic, and it was these quadrupedal features that led some authors hastily to infer that all the trifid impressions were reptilian, or marsupial. The bipedal rows themselves offer two features distinguishing the most nearly-allied forms from the birds: first, the animals took very short steps; and, secondly, the great width of the track-way indicated a very broad body, probably inferior, in delicacy of organization, to that of birds. To these two invariable characters are commonly added a caudal trail, a fourth toe on an occasional front-foot impression, so that the study of a large suite of specimens will satisfy the most truthful observer that these animals were not birds. The total number of species of this character is 21. One of these equalled the largest Brontozoum in size, whose front-foot has not yet been found, though we have indications of a fourth toe behind, and a long, slender tail.
It may not be out of place to allude briefly to the discoveries which have confirmed the existence of the group of ornithic reptiles. The first link in the series was furnished by the discovery of the nearly-complete skeleton of a bird related to the raven in the lithographic stone of the Jurassic series of Bavaria, called the Archeopteryx. A feather belonging to this genus was found in 1861, and described with great minuteness by Hermann von Meyer. Shortly afterward, Andreas Wagner described the nearly-complete skeleton of an animal, to which were attached feathers like the one made known by Von Meyer. He called the animal a flying reptile. Prof. Owen, of the British Museum, made a very thorough examination of the same specimen, and perceived that the feathers corresponded with that named by Von Meyer. It seems to differ in only two particulars from ordinary birds: first, there are two fore-fingers, like hooks, projecting from the wings; and, secondly, the tail is shaped like that of the squirrel, with twenty vertebrae ranged in a line, each with a pair of quill-feathers attached. These variations are not sufficiently great to render it necessary to remove the Archeopteryx from the bird division, but they indicate in
what direction we are to expect a modification of the ornithic type, as it approaches the reptile. And it is in precisely these two respects that the Triassic Herpetoids differ from true birds.
The second link was furnished by the structure of the feet and the ichnites of the Iguanodon in England. Both pairs of limbs were terminated by three-toed feet, often of great size. Only two impressions appear, yet Prof. Owen supposes the tracks of the fore-feet were always covered by the hind-feet. The largest of these impressions are 28 inches long and 25 broad, and the stride sometimes reaches 46 inches. This was the largest of all the English terrestrial herbivorous reptiles, and his impressions have been extensively collected near Hastings.
The third link was furnished by the Hadrosaurus of New Jersey, the American representative of the Iguanodon. He appears to have had the general form of the kangaroo, enormous hind-limbs, terminated by trifid feet; a powerful tail, almost rudimentary anterior extremities, with a skull slightly ornithic, the height of the structure being from 12 to 15 feet. It is singularly like the Ichnozoa Gigantitherium. In fact, if we may follow the fashionable creed of the day, it may be said that the New-Jersey Hadrosaurus was the lineal descendant of the Massachusetts Gigantitherium.
For other links of this series it is only necessary to refer to the late publications of Cope, Huxley, Seely, Owen, Marsh, and other distinguished paleontologists, in which are described nearly a score of kangaroo-like reptiles flourishing, in the later Mesozoic times, in all quarters of the globe. All those new forms present features clearly defining them from both birds on the one hand, and reptiles on the other, so that we are warranted in believing in the existence of genuine birds as well as of ornithic reptiles in ichniferous times.
The Triassic period was par excellence the Age of Reptiles. Besides the Ichnozoa, the museums teem with specimens of fossil bones of various types of Amphibian, Batrachian, Crocodilian, and Lacertilian forms. We should, therefore, naturally expect that a kangaroo-form of body was not indicative of marsupial structure, but rather a modification of reptilian, in the passage, if we may so speak, of the Lacertian to the Ornithic type.
Twenty-one of the Connecticut ichnites have been inferred to the ordinary type of reptiles—the Lacertians—and six to the turtles. Perhaps the number of the former should be increased at the expense of the marsupials and narrow-toed birds. The largest reptile foot is about 15 inches long, three toes in front, curved toward the line of march. It has, besides, a stout thumb, or spur, pointed inwardly. The track-ways of turtles show the trail of the tail, in addition to a pair of feet on both sides.
The group of Amphibians, chiefly batrachians, contains several of interest. Prominent among them is the Otozoum, a track discovered by Mr. Pliny Moody, the first person in the whole world who exhumed an ichnite, so far as has been determined. The animal had a foot 20 inches long, very broad, perhaps web-footed, embracing not less than a square foot of surface. In shape it resembles the Cheirotherium, only it had three fingers instead of four, with a thumb. One species has the thumb recurved, and the other shows it pointed directly forward. The front is about one-third the size of this large hind-foot, and the toes are arranged like those of the front-feet of the Herpetoids. One of the species seems to have had a long, slender tail. This batrachian must have been as large as an elephant, and exceeded in size every other animal among the Ichnozoa. Imagine a frog as large as an elephant, whether announcing the advent of spring by piping, croaking at night in the summer, or taking gigantic leaps after the manner of his modern representatives!
A very important character in the feet of frogs is the possession of pellets, or knobs, instead of claws, at the ends of the toes. These may be observed in the Otozoum, and all the other genera of this group. One genus resembles the Cheirotherium in form, but not in size, having a foot less than an inch long. None have the remarkably long middle toes on the hind-foot, so characteristic of living frogs.
A small, living salamander has the posterior feet pointing back-ward; and, as he walks, the toes point away from the head. The track-way, therefore, consists of two parallel rows of footprints, half of each pointing forward and half directed backward. This salamander has its representative ichnozoan in the Stetiodactylus, not varying essentially in size from it.
One of the most interesting classes of batrachian impressions is called Batrachoides. They consist of numerous saucer-shaped hollows an inch in diameter, crowded together so thickly that the original oval outlines have become pentagonal. Not unfrequently these saucers are arranged in lines and squares, because parallel rows of ripple-marks were occupied by the animals in their construction, often covering several square yards of surface.
Whether arranged in order or clustered helter-skelter, these impressions cannot be distinguished from the mud-nests made every summer by existing tadpoles. Hence it is natural to suppose that the markings made at the different periods were produced by the same agency; and, as we know the origin of the latter, we may infer how the first came upon the rocks. The chief difficulty in the way of accepting this view lies in the perfect resemblance between them. If this doctrine is received, we must believe in the existence of tadpoles in the carboniferous rocks, because they contain similar relics. Those in the Triassic are remarkably distinct, making most beautiful specimens for the show-case.
The reference of the next group to the class of fishes may excite surprise, for it is commonly supposed that these animals never leave the water for the land. It has been ascertained by naturalists that certain varieties of tropical fish often leave the water, and walk, or rather hobble, on the shore, using their fins for legs. This they can do for days together. They have also been known to climb trees in search of sustenance. Their track-way would be peculiar, consisting of two rows of dots or round impressions, made by the prominent sharp spine of the fin, accompanied by various trails produced by the shorter rays, body, and tail. One species of the Ichnozoa has made a trail so much like the markings of these tropical fish that we must believe the Siluridœ had other representatives in the Triassic waters. Another impression seems to have been made by an ordinary fish striking his fins against the ridges between ripple-marks in very shallow water.
With considerable hesitation, thirty-four species of Ichnozoa may be referred to insects. These animals generally have six feet. If attention be paid to the manner in which the common fly walks, it will appear that every foot is brought to the ground, each in a different place, so that every extremity makes a mark. A fly that has been immersed in a colored fluid, and then travels over a sheet of white paper, will leave impressions as distinct as those found upon stone, and the colored track-ways must be our guides to the affinities of the ancient ichnites, like the Copeza.
Between these ancient and modern impressions it is difficult to find marked differences, except of size. Each displays two rows of impressions in groups of three, the several clusters alternating with one another. Of the three marks or lines in each cluster, the inner is almost at right angles with the line of march, the central and outer point backward, the latter the most.
We may suppose that each group of markings was made by the three feet on each side of the animal, the inner impressions by the front pair of limbs, and the outer by the hindmost. Such groups would be preserved only under the most favorable circumstances. In many species the three pairs of legs might be of the same length, and two or more of the feet might tread upon the same spot, leaving but
a single mark. Or the mud may have varied in its capacity for retaining the impressions, so that one or more rows may be wanting. Such cases are common among the Ichnozoa, so that track-ways very dissimilar to the unpractised eye are referred to the same species.
No attempt has been made to refer several ichnitic genera to the several orders of insects. With the small information now existing respecting insectean locomotion, such reference would be premature. It is very obvious that the selection must be made from groups frequenting the sea-shore at low tide.
Considering the lightness of these insects, or whatever animals
they may have been, it is remarkable that any part of these impressions should have been preserved. Only one good locality of them is known, upon a very fine-grained clayey rock, whose liquidity was sufficient to allow the marks to be made, and yet so solid that the heat of the sun evaporated the bulk of the water between the ebb and flow of a single tide. This locality is at the Lily Pond, Turner's Falls, near Greenfield, Massachusetts.
As might be expected, there was a group of Crustaceans, animals who frequent the mud left at low tide. Their impressions have been left on the rocks from the dawn of the Paleozoic age to the very latest period. The famous Prototichnites of Canada upon the Potsdam sandstone, so ably described by Logan and Owen, are generally thought to have been made by gigantic representatives of this class, though hardly by the Pterogotus form, as suggested by Salter and Woodward, because the latter were exclusively swimming animals. The Prototichnites were not represented in the Trias. The forms preserved at Amherst are peculiar, and not to be referred to any special order of Crustacea. One was a giant with a track-way 27 yards wide, and the idea suggested by its inspection is that of an animal with small body stilted high upon very long legs.
Other species of Ichnozoa may have been Annelids, Avith their sinuous, fimbriated line of march, worms, mollusks, with single, double, or treble depressed lines, and various larval forms—whether like those crawling over the surface or making burrows in the mud. A square rod of this Triassic surface will be as thoroughly carved by these various impressions, produced by the lower orders of animal life, as the same surface of the sea-shore in temperate or tropical climes at the present day.
Thus this brief review of the different classes of Triassic Ichnozoa shows a natural assemblage, such as might be found associated in maritime districts. The huge birds associated with kangaroodike forms reminds us immediately of the modern Australian realm, with the cassowaries and the long list of marsupials. Indeed, it would not be strange if the assemblage of life which first showed itself in the American Triassic estuaries had gradually migrated eastward over regions now covered by the Northern Atlantic, pushing farther and farther in each g-eoloscical era till the ultima Thule of Australia is reached, where the modern representatives of the Ichnozoa were prevented from further migration by the termination of continental areas. Soon after its occupation, Australia must have been separated from the Asiatic Continent by a partial submergence, so that the peculiar fauna became restricted, and none of the animals could retrace their steps toward the setting sun, even if they desired. It may be, then, that historic Australia represents Triassic New England in its faunal peculiarities—terrestrial, but not maritime, since marine animals cannot so easily be restricted in their migrations or developments.
Besides footprints, other markings on the Connecticut sandstone attract our attention. We observe the marks of rain-drops, ripples of the waves, shrinkage-cracks, broken bubbles arising from marsh-gas, septaria, rarely a shell, a possible echinoderra, coprolites of birds as determined by chemical analysis, a few reptilian bones, bark and cones of gymnosperms, besides other curious marine and terrestrial plants, remain.
The most interesting of these are the rain-drop impressions, particularly as they indicate the formation of the tracks of animals upon a surface not covered by water. Every rain-drop will leave a single round impression. They are preserved most perfectly when it barely sprinkles. In a heavy or long-continued shower so many impressions are made that they coalesce and leave no distinct trace of their existence. They might be said to resemble a chopped sea. None of the latter could be recognized upon the rock, even if they existed; but the sparsely-scattered impressions are abundantly, oftentimes elegantly, preserved.
Furthermore, when rain-drops are blown by the wind, they must fall upon the mud at an acute angle, greater or less in proportion to the force of the current. When a small stream of water is made to fall upon a hard, fiat surface, it will be deflected, rising at the same angle, thus giving origin to the philosophical statement that the angle of incidence is equal to the angle of reflection. This principle is only partially exemplified by the Triassic phenomena, as the rain-drop is simply elongated in the direction of the wind. But these features illustrate the force and direction of the wind and the amount of the rainfall, so that we see the weather-cock and the rain-gauge of these ancient times. We find the fact impressed upon the strata in the same locality of a change in the course of the wind, showers, and storms, with, of course, intervals of sunshiny weather. Surely, then, the primitive times witnessed the same alternations of storm and sunshine that prevail at present.
The technical department of the science of Ichnology relates to a discussion of the characters derived from locomotion peculiar to each division of the animal kingdom. Certain distinctions are very obvious, such as the peculiarities of bipedal, quadrupedal, and multipedal locomotion. Bipedal tracks are chiefly of man, birds, and occasionally of the kangaroo-forms. So readily can these be distinguished that definitions are superfluous. The quadrupeds display hand-like feet, as the monkeys, rounded toes and heels like the dog, hoofs either single or cloven, and long, slender toes, few or numerous. Others, like the turtle and lizards, would show two rows of impressions, with short or long steps, and an occasional caudal mark. The lower forms of life would display a great variety of trails, loops, and hops; raised burrows in the mud, or vertical holes, and others of endless diversity. It is unnecessary to specify further the various locomotive characters by which the different groups may be recognized. That such exist may be considered as proved—some of them of very precise application. Not less than thirty different locomotive characters are made use of in the description of the New England ichnitic fauna. Further investigations must add to their number and definiteness, and consequently to the value of ichnological studies.
Cuvier has finely described the definiteness and certainty with which we can infer the character of an animal from its track, though, when he wrote, fossil foot-marks were unknown. "Any one," says he, "who observes merely the print of a cloven hoof, may conclude that it has been left by a ruminant animal, and regard the conclusion as equally certain with any other in physics or morals. Consequently, this single footmark clearly indicates to the observer the forms of the teeth, of all the leg-bones, thighs, shoulders, and of the trunk of the body of the animal which left the mark. It is much surer than all the marks of Zadig."
The contemplation of fossil foot-marks may suggest important moral lessons. To leave their names inscribed on the world's history is a universal desire of mankind. To accomplish this object, various methods have been devised; comfort, health, life, and even moral principle, have been sacrificed, and yet the actor has been unable to crawl into the remotest corner of history. There have been conquerors bathing their limbs in the blood of the slain; kings, who have erected towers, pyramids, and cities; authors, who have composed elaborate and learned treatises; gigantic intellects, who have moulded the characters of nations—and yet no traces of their individual names or memories remain to posterity. All of these may have spurned the reptiles crawling beneath their feet; yet the lower orders of animal life—such as flourished hundreds of thousands of years since, before the surface of the earth was fitted for the residence of man—have left memorials of their passage enduring and indelible.
Those who would benefit their fellow-men need not despair. Those senseless tribes had only dead matter to work upon, and the touch of a hammer may ruthlessly destroy what has endured for ages, and it can never be repaired. But man can influence the living mind, imparting lessons that will outlast, in their influence, both time and fate. Then let all our actions be upright, and we shall thus—
——"departing, leave behind us
Footprints on the sands of time."