Chapter 13

Fig. 81.—Skull of the Man of Spy. (From photograph.)

Upon extending inquiries, it was found that the Neanderthal type of skull is one which still has representatives in all nations; so that it is unsafe to infer that the individual was a representative of all the individuals living in his time. The skull of Bruce, the celebrated Scotch hero, was a close reproduction of the Neanderthal type; while, according to Quatrefages,[DH]the skull of the Bishop of Toul in the fourth century “even exaggerates some of the most striking features of the Neanderthal cranium. The forehead is still more receding, the vault more depressed, and the head so long that the cephalic index is 69-41.” The discovery of Messrs. Fraipont and Lohest addsmuch to our definite knowledge of the Neanderthal type of man, since the Belgic specimens are far more complete than any others heretofore found, there being in their collection two skulls, together with the jawbones and most of the other parts of the frame. In this case also there is no suspicion that the deposits had been disturbed, so as to admit any intrusion of human relics into the company of relics of an earlier age. According to M, Lohest, there were three distinct ossiferous beds, separated by layers of stalagmite. All the ossiferous beds contained the remains of the mammoth, but in the upper stratum they were few, and probably intrusive. The implements found in this were also of a more modern type. In the second stratum from the top numerous hearths were found with burnt wood and ashes, together with the bones of the rhinoceros, thehorse, the mammoth, the cave-bear, and the cave-hyena, all of which were abundant, while there were also specimens of the Irish elk, the reindeer, the bison, the cave-lion, and several other species. In this layer also there were numerous implements of ivory, together with ornaments and some faint indications of carving upon the rib of a mammoth, besides a few fragments of pottery.

[DH]Human Species, p. 310,

It was in the third, or lowest, of these beds that the skeletons were found. Here they were associated with abundant remains of the rhinoceros, the horse, the bison, the mastodon, the cave-hyena, and a few other extinct species. Flint implements also, of the “Mousterien” pattern (which, according to the opinion of the French archæologists, is characteristic of middle palæolithic times), were abundant Neither of the skeletons was complete, but they were sufficiently so to give an adequate idea of the type to which they belong, and one of the skulls is nearly perfect. According to M. Fraipont, “one of these skulls is apparently that of an old woman, the other that of a middle-aged man. They are both very thick; the former is clearly dolichocephalic (long-headed, index 70), the other less so. Both have very prominent eyebrows and large orbits, with low, retreating foreheads, excessively so in the woman. The lower jaws are heavy. The older has almost no projecting chin. The teeth are large, and the last molar is as large as the others. These points are characteristic of an inferior and the oldest-known race. The bones indicate, like those of the Neanderthal and Naulette specimens, small, square-shouldered individuals.” They were “powerfully built, with strong, curiously curved thigh-bones, the lower ends of which are so fashioned that they must have walked with a bend at the knees.”[DI]

[DI]Huxley, Nineteenth Century, vol. xxviii (November, 1890), p. 774.

Other crania from various Quaternary deposits in Europe seem to warrant the inference that this type of man was the prevalent one during the early part of the Palæolithic age. As long ago as 1700 a skull of this type was exhumed in Canstadt, a village in the neighbourhood of Stuttgart, in Würtemberg. This was found in coexistence with the extinct animals whose bones we have described as so often appearing in the high-level river-gravel of the Glacial age. But the importance of the discovery at Canstadt was not appreciated until about the middle of the present century. From the priority of the discovery, and of the discussion among German anthropologists concerning it, it has been thought proper, however, by some to give the name of this village to the race and call it the “Canstadt race.” But, whatever name prevails, it is important in our reading to keep in mind that the man of Canstadt, the man of Neanderthal, and the man of Spy are identical in type, and probably in age. Similar discoveries have been made in various other places. Among these are a lower jaw of the same type discovered in 1865 by M. Dupont, at Naulette, in the valley of the Lesse, in Belgium, and associated with the remains of extinct animals; a jawbone found in a grotto at Arcy; a fragment of a skull found in 1865 by Faudel, in the loess of Eguisheim, near Colmar; a skull at Olmo, discovered in 1863, in a compact clayey deposit forty-five feet below the surface; and a skull discovered in 1884 at Marcilly.

M. Dupont has brought to light much additional testimony to glacial man from other caves in different parts of Belgium. In all he has explored as many as sixty. Three of these, in the valley of the Montaigle, situated about one hundred feet above the river, contained both remains of man and many bones of the mammoth and other associated animals, which had evidently been brought in for food.

In the hilly parts of Germany, also, and in Hungary,and even in the Ural Mountains in Russia, and in one of the provinces of Siberia, the remains of the rhinoceros, and most of the other animals associated with man in glacial times, have been found in the cave deposits which have been examined. Though it can not be directly proved that these animals were associated with man in any of these places, still it is interesting to see how wide-spread the animals were in northern Europe and Asia during the Glacial period.

Some northern animals, also, spread at this time into southern Europe—remains of the reindeer having been discovered on the south slope of the Pyrenees, but the remains of the mammoth, the woolly rhinoceros, and the musk ox, have not been found so far south.

African species of the elephant, however, seem at one time to have had free range throughout Spain, and the hippopotamus roamed in vast herds over the valleys of Sicily, while several species of pygmy elephants seem to be peculiar to the island of Malta.

In the case of all the cave deposits referred to (with possibly the exception of those of Victoria, England, and Cae Gwyn, Wales), the evidence of man’s existence during the Glacial period is inferential, and consists largely in the fact that he was associated with various extinct animals which did not long survive that period, or with animals that have since retired from Europe to their natural habitat in mountain-heights or high latitudes. The men whose remains are found in the high-level river-drift, and in the caverns described, were evidently not in possession of domestic animals, as their bones are conspicuous for their absence in all these places. The horse, which would seem to be an exception, was doubtless used for food, and not for service.

If we were writing upon the general subject of the antiquity and development of the human race, we should speak here in detail of several other caves and rock sheltersin France and southern Europe, where remains of man belonging to an earlier period have been found. We should mention the rock shelter of Cro-Magnon in the valley of Vezère, as well as that of Mentone, where entire human skeletons were found. But it is doubtful if these and other remains from caves which might be mentioned belong in any proper sense to the Glacial period. The same remarks should be made also with reference to the lake-dwellings in Switzerland, of which so much has been written in late years. All these belong to a much later age than the river-drift man of whom we are speaking, and of whom we have such abundant evidence both in Europe and in America.

Fig. 82.—Tooth of Machairodus neogæus, ×16(drawn from a cast).Fig. 83.—Perfect tooth of an Elephas, found in Stanislaus County, California,18natural size.

Extinct Animals associated with Man during the Glacial Period.

This is the proper place in which to speak more fully of the extinct animals which accompanied man in his earliest occupation of Europe and America, and whose remains are so abundant in the river-drift gravel and in the caves of England, in connection with the relics of man. Among these animals are

The Lion, which is now confined, to Africa and the warmer portions of Asia. But in glacial times a large species of this genus ranged over Europe from Sicily to central England.

The saber-toothed Tiger, with tusks ten inches long: (Machairodus latidens), is now extinct. This species was in existence during the latter part of the Tertiary period, but continued on until after man’s appearance in the Glacial period. The presence of this animal would seem to indicate a warm climate.

The Leopard (Felis pardus) is now confined to Africa and southern Asia, and the larger islands adjoining; but during man’s occupation of Europe in the Glacial epoch he was evidently haunted at every step by this animal; for his bones are found as far north in England as palæolithic man is known to have ranged.

The Hyena. Two species of this animal are found in the bone-caves of Europe. During the Glacial epoch they ranged as far up as northern England, but they are now limited to Africa and southwestern Asia.

Fig. 84.—Skull ofHyena spelæa, ×14.

The Elephant is represented in the Preglacial and Glacial epochs by several species, some of which ranged as far north as Siberia. The African elephant is not now found north of the Pyrenees and the Alps. But a species ofdwarf elephant, but four or five feet in height, has already been referred to as having occupied Malta and Sicily; and still another species has been found in Malta, whose average height was less than three feet. An extinct species (Elephas antiquus), whose remains are found in the river-drift and in the lower strata of sediment in many caverns as far north as Yorkshire, England, was of unusual size, and during the Glacial period was found on both sides of the Mediterranean. But the species most frequently met with in palæolithic times was the mammoth (Elephas primigenius). This animal, now extinct, accompanied man in nearly every portion both of Europe and North America, and lingered far down into post-glacial times before becoming extinct. This animal was nearly twice the weight of the modern elephant, and one third taller. Occasionally his tusks were more than twelve feet long, and curved upward in a circle. It is the carcasses of this animal which have been found in the frozen soil of Siberia and Alaska. It had a thick covering of long, black hair, with a dense matting of reddish wool at the roots. During the Glacial period these animals must have roamed in vast herds over the plains of northern France and southern England, and the northern half of North America.

Fig. 85.—Celebrated skeleton of mammoth, in St. Petersburg museum.

Fig. 86.—Molar tooth of mammoth (Elephas primigenius):a, grinding surface;b, side view.

The Hippopotamus is at present a familiar animal in the larger rivers of Africa, but is not now found in Europe. During the Glacial period, however, he ranged as far north as Yorkshire, England, and his remains were found in close association with those of man, both in Europe and on the Pacific coast in America. Twenty tons of their bones have been taken from a single cave in Sicily.[DJ]

[DJ]Prestwich’s Geology, vol. ii, p. 508.

Fig. 87.—Tooth ofMastodon Americanus.

The mammoth and the rhinoceros we know to have been adapted to cold climates by the possession of long hair and thick fur, but the hippopotamus by its love for water would seem to be precluded from the possession of this protective covering.It is suggested, however, by Sir William Dawson, that he may have been adapted to arctic climates by a fatty covering, as the walrus is at the present time. A difficulty in accounting for many of the remains of the hippopotamus in some of the English caverns is that they are so far away from present or possible water-courses. But it would seem that due credit has not been ordinarily given to the migratory instincts of the animal. In southern Africa they are known to “travel speedily for miles over land from one pool of a dried-up river to another; but it is by water that their powers of locomotion are surpassingly great, not only in rivers, but in the sea.... The geologist, therefore, may freely speculate on the time when herds of hippopotami issued from North African rivers, such as the Nile, and swam northward in summer along the coasts of the Mediterranean, or even occasionally visited islands near the shore. Here and there they may have landed to graze or browse, tarrying awhile, and afterwards continuing their course northward. Others may have swum in a few summer days from rivers in the south of Spain or France to the Somme, Thames, or Severn, making timely retreat to the south before the snow and ice set in.”[DK]

[DK]Lyell, Antiquity of Man, p. 180,

The Mastodon (Mastodon Americanus), (Fig. 88), “is probably the largest land mammal known, unless we except the Dinotherium. It was twelve to thirteen feet high, and, including the tusks, twenty-four to twenty-five feet long. It differed from the elephant chiefly in the character of its teeth. The difference is seen in Figs. 86 and 87. The elephant’s tooth given above (Fig. 86) is sixteen inches long, and the grinding surface eight inches by four.”

Fig. 88.—Mastodon Americanus(after Owen).

The mastodon, together with the mammoth, made their appearance about the middle of the Miocene epoch. At the close of the Tertiary period the mastodon became extinct on the Eastern Continent, but continued in North America to be a companion of man well on toward the close of the Glacial period. Many perfect skeletons have been found in the deposits of this period in North America. “One magnificent specimen was found in a marsh near Newburg, New York, with its legs bent under the body, and the head thrown up, evidently in the very position in which it mired. The teeth were still filled with the half-chewed remnants of its food, which consisted of twigs of spruce, fir, and other trees; and within the ribs, in the place where the stomach had been, a large quantity of similar material was found.”[DL]

[DL]Le Conte’s Geology (edition of 1891), p. 582.

Fig. 89.—Skeleton ofRhinoceros tichorhinus.

The Rhinoceros is now confined to Africa and southernAsia; but the remains of four species have been found in America, Europe, and northern Asia, in deposits of the Glacial period. In company with that of the mammoth, already spoken of, a carcass of the woolly rhinoceros was found in 1771 in the frozen soil of northern Siberia. The bones of other species have been found as far north as Yorkshire, England. In the valley of the Somme there was found “the whole hind limb of a rhinoceros, the bones of which were still in their true relative position. They must have been joined together by ligaments and even surrounded by muscles at the time of their interment.” An entire skeleton was found near by. The gravel terrace in which these occurred is about forty feet above the floor of the valley, and must have been formed subsequent to some of the strata which contained the remains of human art. In America the bones are found in the gold-bearing gravels of California, in connection with human remains.

Fig. 90.—Skull of cave-bear (Ursus spelæus),

The Bear was represented in Europe in palæolithic times by three species, of which only one exists there atthe present time. But during the Glacial period the grizzly bear, now confined to the western part of America, and the extinct cave-bear were companions, or enemies as the case may be, of man throughout Europe. The cave-bear was of large size, and his bones occur almost everywhere in the lower strata of sediment in the caves of England.

The Great Irish Elk, or deer, is now extinct, though it is supposed by some to have lingered until historic times. Its remains are found widely distributed over middle Europe in deposits of palæolithic age.

Fig. 91.—Skeleton of the Irish elk (Cervus megaceros).

The Horse was also, as we have seen, a very constant associate of man in middle Europe during the Palæolithic age, but probably not as a domesticated animal. The evidence is pretty conclusive that he was prized chiefly for food. About some of the caves in France such immense quantities of their bones are found that they can be accounted for best as refuse-heaps into which the useless bones had been thrown after their feasts, after the manner of the disposal of shells of shell-fish. In America the horses associated with man were probably of a species now extinct. The skull of one (Equus excelsus) recently found in Texas, in Pleistocene deposits, associated with human implements, is, according to Cope, intermediate in character between the horse and quagga.[DM]The frontal bone was crushed in in a manner to suggest that it had been knockedin the head with a stone hammer, such as was found in the same bed. Possibly, therefore, man’s love of horse-flesh may have been an important element in securing the extinction of the species in America.

[DM]American Naturalist, vol. xxv (October, 1891), p. 912.

Besides these animals there were associated with man at this time the Musk Sheep and the Reindeer, both now confined to the regions of the far north, but during the Glacial period ranging into southern France, and mingling their bones with those both of man and of the southern species already enumerated.

Fig. 92.—Musk-sheep (Ovibos moschatius).

The Wolverine, the Arctic Fox, the Marmot, the Lemming—all now confined to colder regions—at that time mingled on the plains of central Europe with the species mentioned as belonging now to Africa and southern Asia. The Ibex, also, and the Snowy Vole and Chamois descended to the plains from their mountain-heights, and joined in the strange companionship of animals from the north and from the south.

Besides these extremes there were associated with man during the Glacial period numerous representatives of the temperate group of existing animals, such as the bison, the horse, the stag, the beaver, the hare, the rabbit, theotter, the weasel, the wild-cat, the fox, the wolf, the wild boar, and the brown bear.

Fig. 93.—Reindeer.

To account for this strange intermingling of arctic and torrid species of animals, especially in Europe, during man’s occupancy of the region in glacial times, various theories have been resorted to, but none of them can be said to be altogether satisfactory. One hypothesis is that the bones of these diverse animals became mingled by reason of the great range of the annual migration of the species. The reindeer, for example, still performs extensive annual migrations. In summer it ventures far out upon thetundrasof North America and Siberia to feed upon the abundant vegetation that springs up like magic under the influence of the long days of sunshine; while, as winter approaches, it returns to the forests of the interior. Or in other places this animal and his associates, like birds of passage, move northward in summer to escape the heat, and southward in the winter to escape the extreme cold. Many of the other animals also are more or less migratory in their habits.

Thus it is thought that during the Glacial period, when man occupied northern France and southern England, the reindeer, the musk sheep, the arctic fox, and perhaps the hippopotamus and some other animals, annually vibrated between northern England and southern France, a slight elevation of the region furnishing a land passage from England to the continent; while the chamois and other Alpine species vibrated as regularly between the valleys in winter and the mountain-heights in summer. The habits of these species are such that it is not difficult to see how in their case this migration could have taken place.

Professor Boyd Dawkins attempts to reduce the difficulty by supposing that the Glacial epoch was marked by the occurrence of minor periods of climatic variation, during which, in comparatively short periods, the isothermal lines vibrated from north to south, andvice versa. In this view the southern species gradually crowded upon the northern during the periods of climatic amelioration, until they reached their limit in central England, and then in turn, as the climate became more rigorous, slowly retreated before the pressure of their northern competitors. Meanwhile the hyena sallied forth from his various caves, over this region, at one time of the year to feed upon the reindeer, and at another time of the year upon the flesh of the hippopotamus, in both cases dragging their bones with him to his sheltered retreat in the limestone caverns[DN]which he shared at intervals with palæolithic man.

[DN]Early Man in Britain, p. 114.

The theory of Mr. James Geikie is that the period, while one of great precipitation, was characterised by a climate of comparatively even temperature, in which there was not so great a difference as now between the winters and the summers, the winters not being so cold and the summers not so hot as at present. This is substantially the condition of things in southern Alaska at the present time, where extensive glaciers come down to the sea-level, even though the thermometer at Sitka rarely goes below zero (Fahrenheit). It is, therefore, easy to conceive that if there were extensive plains bordering the Alaskan archipelago, so as to furnish ranging grounds for more southern species, the animals of the north and the animals of the south might partially occupy the same belt of territory, and their bones become mingled in the same river deposits.

In order to clear the way for either of these hypotheses to account for the mingling of arctic and torrid speciescharacteristic of the period under consideration in Europe, we must probably suppose such an elevation of the region to the south as to afford land connection between Europe and Africa. This would be furnished by only a moderate amount of elevation across the Strait of Gibraltar and from the south of Italy to the opposite shore in Africa; and there are many indications, in the distribution of species, of the existence in late geological times of such connection.

It should also be observed that the present capacities and habits of species are not a certain criterion of their past habits and capacities. As already remarked, both the rhinoceros and the mammoth of glacial times were probably furnished with a woolly protection, which enabled them to endure more cold than their present descendants could do, while the elephant is even now known to be able to endure the rigors of the climate at great elevations upon the Himalaya Mountains. We can easily imagine these species to have been adjusted to quite different climatic conditions from those which now seem necessary to their existence. In the case of the hippopotamus, also, it is quite possible, as already suggested, that it is more inclined to migration than is generally supposed.

Geikie’s theory of the prevalence of an equable climate during a portion of the Glacial period in Europe is thought to be further sustained by the character of the vegetation which then covered the region, as well as by the remains of the mollusks which occupied the waters. Then “temperate and southern species like the ash, the poplar, the sycamore, the fig-tree, the Judas-tree, the laurel, etc., overspread all the low ground of France, as far north at least as Paris.... It was under such conditions,” continues Geikie, "that the elephants, rhinoceroses, and hippopotamuses, and the vast herds of temperate cervine and bovine species ranged over Europe, from the shores of the Mediterranean up to the latitude of Yorkshire,and probably even farther north still; and from the borders of Asia to the Western Ocean. Despite the presence of numerous fierce carnivora—lions, hyenas, tigers, and others—Europe at that time, with its shady forests, its laurel-margined streams, its broad and deep-flowing rivers, a country in every way suited to the needs of a race of hunters and fishers—must have been no unpleasant habitation for palæolithic man.

“This, however, is only one side of the picture. There was a time when the climate of Pleistocene Europe presented the strongest contrast to those genial conditions—a time when the dwarf birch of the Scottish Highlands, and the arctic willow, with their northern congeners, grew upon the low grounds of middle Europe. Arctic animals, such as the musk sheep and the reindeer, lived then, all the year round, in the south of France; the mammoth ranged into Spain and Italy; the glutton descended to the shores of the Mediterranean; the marmot came down to the low grounds at the foot of the Apennines; and the lagomys inhabited the low-lying maritime districts of Corsica and Sardinia. The land and fresh-water shells of many Pleistocene deposits tell a similar tale; boreal, high alpine, and hyperborean forms are characteristic of these accumulations in central Europe; even in the southern regions of our continent the shells testify to a former colder and wetter climate.”[DO]

[DO]Prehistoric Europe, p. 67.

In Mr. Geikie’s view these facts indicate two Glacial periods, with an intervening epoch of mild climate. In the opinion of others they are readily explainable by the coming on and departure of a single Ice age, with its various minor episodes.

Earliest Remains of Man on the Pacific Coast of North America.

Most interesting evidence concerning the antiquity of man in America, and his relation to the Glacial period, has come from the Pacific coast. During the height of the mining activity in California, from 1850 to 1860, numerous reports were rife that human remains had been discovered in the gold-bearing gravel upon the flanks of the Sierra Nevada Mountains. These reports did not attract much scientific attention until they came to relate to the gravel deposits found deeply buried beneath a flow of lava locally known as the Sonora or Tuolumne Table Mountain. This lava issued from a vent near the summit of the mountain-range, and flowed down the valley of the Stanislaus River for a distance of fifty or sixty miles, burying everything in the valley beneath it, and compelling the river to seek another channel. The thickness of the lava averages about one hundred feet, and so long a time has elapsed since the eruption that the softer strata on either side of the valley down which it flowed have been worn away to such an extent that the lava now rises nearly everywhere above the general level, and has become a striking feature in the landscape, stretching for many miles as a flat-topped ridge about half a mile in width, and presenting upon the sides a perpendicular face of solid basalt for a considerable distance near the lower end of the flow.

Fig. 94.—Section across Table Mountain, Tuolumne County, California:L, lava;G, gravel;S, slate;R, old river-bed;R′, present river-bed.

Fig. 95.—Calaveras Skull. (From Whitney.)

It was under this mountain of lava that the numerous implements and remains of man occurred which were reported to Professor J. D. Whitney when he was conducting the geological survey of California between 1860 and 1870. The implements consisted of stone mortars and pestles, suitable for use in grinding acorns and other coarse articles of food. There were, however, some rude articles of ornament. In one of the mining shafts penetratingthe gravel underneath Table Mountain, near Sonora, there was reported to have been discovered, in 1857, a human jawbone, one portion of which was sent by responsible parties to the Boston Society of Natural History, and another part to the Philadelphia Academy of Sciences, in whose collections the fragments can now be seen.

Interest reached a still higher pitch when, in 1860, an entire human skull with some other human bones was reported to have been discovered under this same lava deposit, a few miles from Sonora, at Altaville, in Calaveras County, and hence known as the “Calaveras skull.” Persistent efforts were made soon after to discredit the genuineness of this discovery. Bret Harte showered upon it the shafts of his ridicule, and various other persons gave currency to the story that the whole report originated in a joke played by the miners upon unsuspecting geologists. These attacks were so successful that many conservative archæologists and men of science have refused to accept the skull as genuine.

Recent events, however, have brought such additional evidence[DP]to the support of this discovery that it would seem unreasonable any longer to refuse to credit the testimony. At the meeting of the Geological Society of America, at Washington, in January, 1891, Mr. George P. Becker, of the United States Geological Survey, who for some years has had charge of investigations relating to the gold-bearing gravels of the Pacific coast, presented the affidavit of Mr. J. H. Neale, a well-known mining engineer of unquestionable character, stating that he had taken a stone mortar and pestle, together with some spear-heads (which through Mr. Becker he presented to the Society), from undisturbed strata of gravel underneath the lava of Table Mountain, near Rawhide Gulch, a fewmiles from Sonora. At the same meeting Mr. Becker presented a pestle which Mr. Clarence King, the first director of the United States Geological Survey, took with his own hands out of undisturbed gravel under this same lava deposit, near Tuttletown, a mile or two from the preceding locality mentioned.

[DP]See Bulletin Geological Society of America, 1891, pp. 189-200.

I was so fortunate, also, as to be able to report to the Society at the same meeting the discovery, in 1887, of a small stone mortar by Mr. C. McTarnahan, the assistant surveyor of Tuolumne County. This mortar was found by Mr. McTarnahan in the Empire mine, which penetrates the gravel underneath Table Mountain, about three miles from Sonora, and not far from the other localities above mentioned. The place where the mortar was found is about one hundred and seventy-five feet in from the edge of the superincumbent lava, which is here about one hundred feet in thickness. At my request, this mortar was presented by its owner, Mrs. M. J. Darwin, to the Western Reserve Historical Society of Cleveland, Ohio, in whose collection it can now be seen.

These three independent instances, each of them authenticated by the best of evidence, have such cumulative force that probably few men of science will longer stand out against it.

Associated with these discoveries, there is to be mentioned another, which was brought to my notice by Mr. Charles Francis Adams in October, 1889.[DQ]This was a miniature clay image of a female form, about one inch and a half in length, and beautifully formed, which was found, in August, 1889, by Mr. M. A. Kurtz, while boring an artesian well at Nampa, Ada County, Idaho. The strata passed through included, near the surface, fifteen feet of lava. Underneath this, alternating beds of clay andquicksand occurred to a depth of three hundred and twenty feet, where there appeared indications of a former surface soil lying just above the bed-rock, from which the clay image was brought up in the sand-pump.

[DQ]See Proceedings Boston Society Natural History, January, 1890, and February, 1891.

Fig. 96.—Three views of Nampa image drawn to scale. The middle one is from a photograph.

I devoted the summer of 1890 to a careful study of the lava deposits both in Idaho and in California, with a view to learning their significance with reference to these discoveries. The main facts brought to light by this investigation are that in the Snake River Valley, Idaho, there are not far from twelve thousand square miles of territory covered with a continuous stratum of basaltic lava, extending nearly across the entire diameter of the State from east to west. Nampa, where the miniature image was discovered, is within five miles of the western limit of this lava-flow, and where it had greatly thinned out. The relative age of the lava is shown by its relation to Tertiary beds of shale and sandstone, containing numerous fossils of late Pliocene species. These are overlaid in this vicinity by the lava, thus determining its post-Tertiary character. Examination with reference to the more precise determination of age reveals channels of erosion formed since the lava-flow took place, which, when studied sufficiently, will probably lead to valuable approximateresults. At present I can only say that the amount of erosion since the lava eruptions of western Idaho is not excessive, and very likely may be brought within a period of from ten thousand to twenty thousand years. The enormous erosion in the cañon of the Snake River, near Shoshone Falls, in central Idaho, is doubtless of a much earlier date than that in the Boise River, near Nampa.

Fig. 97.—Map showing Pocatello, Nampa, and the valley of Snake River.

The disturbances created in this part of the valley by the bursting of the barriers between the glacial Lake Bonneville and the Snake River, already described (see above,page 233), have not been worked out. There can be no doubt, however, that interesting results will come to light in connection with the problem; for Pocatello, the point at which thedébâclereached the Snake River plain, is about 2,000 feet higher than Nampa, and 350 miles distant, and the water must have poured into the valley faster than the river in its upper portion could have discharged it. By just what channels the mighty current worked down to the lower levels on the western borders of the State it would be most interesting as well as instructive to know.

A study of the situation in Tuolumne and CalaverasCounties, California, reveals a state of things closely resembling, in important respects, that in western Idaho. At first sight the impression is made that an immense lapse of time must have occurred since the volcanic eruption which furnished the lava of Table Mountain. The Stanislaus River flows in a channel of erosion a thousand feet or more lower than the ancient channel filled by lava, and in two or three places cuts directly across it. An immense amount of time, also, would seem to be required to permit the smaller local streams to have worn away so much of the sides of the ancient valley as to allow the lava deposit now so continuously to rise above the general surface. Still, the question of absolute time cannot be considered separately without much further study. It is by no means certain that, when the lava-stream poured down the mountain, it always followed the lowest depressions; but at certain points it may have been dammed up in its course by its own accumulations so as to be turned off into what was then an ancient abandoned channel.

Fig. 98.—Section along the line, north and south:r′ r′, old river-beds;r r, present river-beds;L, lava;sl, slate.

The forms of animal and vegetable life with which the remains of man under Table Mountain are associated, are, indeed, to a considerable extent, species now extinct in California, and some of them no longer exist anywhere in the world. But a suggestion of Professor Prestwich, in England, made with reference to the extinct forms of life associated with human remains in the glacial deposits in Europe, is revived by Mr. Becker, of the Geological Survey, with reference to the California discoveries; hisinference being, not that man is so extremely ancient in California, but that many of these plants and animals have continued to a more recent date than has ordinarily been supposed.

The connection of these lava-flows on the Pacific coast with the Glacial period is unquestionably close. For some reason which we do not fully understand, the vast accumulation of ice in North America during the Glacial period is correlated with enormous eruptions of lava west of the Rocky Mountains, and, in connection with these events, there took place on the Pacific coast an almost entire change in the plants and animals occupying the region. Mr. Warren Upham is of the opinion that on the Pacific coast they lingered much later than in the region east of the Rocky Mountains. Indeed, it is pretty certain that not many centuries have elapsed since the glacial phenomena of the Sierra Nevada Mountains were much more pronounced than they are at the present time, and it is equally certain that there have been vast eruptions of lava in California within three hundred years.

From these data, therefore, Mr. Becker has real foundation for his suggestion that perhaps in the Glacial period California was a kind of health resort for Pliocene animals, as it is at the present time for man; or, at any rate, that the later date of the accumulations permitted the animals to survive there much longer than in the region east of the Rocky Mountains.

Further discussion of the preceding facts will profitably be deferred until, in the next two chapters, the questions of the cause and date of the Glacial period have been considered.

CHAPTER IX.

THE CAUSE OF THE GLACIAL PERIOD.

In searching for the cause of the Glacial period, it is evident that we must endeavor to find conditions which will secure over the centre of the glaciated area either a great increase of snow-fall or a great decrease in the mean annual temperature, or both of these conditions combined in greater or less degree. As can be seen, both from the nature of the case and from the unglaciated condition of Siberia and northern Alaska, a low degree of temperature is not sufficient to produce permanent ice-fields. If the snow-fall is excessively meagre, even the small amount of heat in an arctic summer will be sufficient to melt it all away.

From the condition of Greenland, however, it appears that a moderate amount of precipitation where it is chiefly in the form of snow may produce enormous glaciers if at the same time the average temperature is low. In southeastern Alaska, on the other hand, the glaciers are of enormous size, though the mean annual temperature is by no means low, for there the great amount of snow-fall amply compensates for the higher temperature.

Snow stores the cold and keeps it in a definite place. If the air becomes chilled, circulation at once sets in, and the cold air is transferred to warmer regions; but if there is moisture in the air, so that snow forms, the cold becomes locked up, as it were, and falls to the earth.

The amount of cold thus locked up in snow is enormous.To melt one cubic foot of ice requires as much heat as would raise the temperature of a cubic foot of water 176° Fahrenheit. To melt a “layer of ice only one inch and a half thick would require as much heat as would raise a stratum of air eight hundred feet thick from the freezing-point to the tropical heat of 88° Fahrenheit.” It is the slowness with which ice melts which enables it to accumulate as it does, both in winter and upon high mountains and in arctic regions. Captain Scoresby relates that when near the north pole the sun would sometimes be so hot as to melt the pitch on the south side of his vessel, while water was freezing on the north side, in the shade, owing to the cooling effect of the masses of ice with which he was surrounded.

Thus it will appear that a change in the direction of the moist winds blowing from the equator towards the poles might produce a Glacial epoch. If snow falls upon the ocean it cools the water, but through the currents, everywhere visible in the sea, the temperature in the water in the different parts soon becomes equalized. If, however, the snow falls upon the land, it must be melted by the direct action of the sun and wind upon the spot where it is. If the heat furnished by these agencies is not sufficient to do it year by year, there will soon be such an accumulation that glaciers will begin to form. It is clear, therefore, that the conditions producing a Glacial period are likely to prove very complicated, and we need not be surprised if the conclusions to which we come are incapable of demonstration.

Theories respecting the cause of the Glacial period may be roughly classified as astronomical and geological. Among the astronomical theories, one which has sometimes been adduced is that the solar system in its movement through space is subjected to different degrees of heat at different times. According to this theory, the temperate climate which characterised the polar regionsduring the Tertiary period, and continued up to the beginning of the Glacial epoch, was produced by the influence of the warmer stretches of space through which the whole solar system was moving at that time; while the Glacial period resulted from the influence upon the earth of the colder spaces through which the system subsequently moved.

While it is impossible absolutely to disprove this hypothesis, it labors under the difficulty of having little positive evidence in its favor, and thus contravenes a fundamental law of scientific reasoning, that we must have a real cause upon which to rest our theories. In endeavouring to explain the unknown, we should have something known to start with. But in this case we are not sure that there are any such variations in the temperature of the space through which the solar system moves. This theory, therefore, cannot come in for serious consideration until all others have been absolutely disproved. As we shall also more fully see, in the subsequent discussion, the distribution of the ice during the Glacial period was not such as to indicate a gradual extension of it from the north pole, but rather the accumulation upon centres many degrees to the south.

Closely allied with the preceding theory is the supposition broached by some astronomers that the sun is a variable star, dependent to some extent for its heat upon the impact of meteorites, or to the varying rapidity with which the contraction of its volume is proceeding.

It is well known that when two solid bodies clash together, heat is produced proportionate to the momentum of the two bodies. In other words, the motion which is arrested is transformed into heat. Mr. Croll, in his last publication[DR]upon the subject, ingeniously attempted to account for the gaseous condition of the nebulæ and theheat of the sun and other fixed stars by supposing it to be simply transformed motion. According to this theory, the original form of force imparted to the universe was that exerted in setting in motion innumerable dark bodies, which from time to time have collided with each other. The effects of such collisions would be to transform a large amount of motion into heat and its accompanying forms of molecular force. The violence of the compact of two worlds would be so great as to break them up into the original atoms of which they are composed, and the heat set free would be sufficient to keep the masses in a gaseous condition and cause them to swell out into enormous proportions. From that time on, as the heat radiated into space, there would be the gradual contraction which we suppose is going on in all the central suns, accompanied, of course, with a gradual decline of the heat-energy in the system.

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