(From the Voyage of the Challenger.) By
SIR C. WYVILLE THOMSON, KT., LL.D., ETC.
I think the Painter's Vale cave is the prettiest of the whole. The opening is not very large. It is an arch over a great mass of débris forming a steep slope into the cave, as if part of the roof of the vault had suddenly fallen in. At the foot of the bank of débris one can barely see in the dim light the deep clear water lying perfectly still and reflecting the roof and margin like a mirror. We clambered down the slope, and as the eye became more accustomed to the obscurity the lake stretched further back. There was a crazy little punt moored to the shore, and after lighting candles Captain Nares rowed the Governor back into the darkness, the candles throwing a dim light for a [pg 112] time—while the voices became more hollow and distant—upon the surface of the water and the vault of stalactite, and finally passing back as mere specks into the silence.
After landing the Governor on the opposite side, Captain Nares returned for me, and we rowed round the weird little lake. It was certainly very curious and beautiful; evidently a huge cavity out of which the calcareous sand had been washed or dissolved, and whose walls, still to a certain extent permeable, had been hardened and petrified by the constant percolation of water charged with carbonate of lime. From the roof innumerable stalactites, perfectly white, often several yards long and coming down to the delicacy of knitting-needles, hung in clusters; and wherever there was any continuous crack in the roof or wall, a graceful, soft-looking curtain of white stalactite fell, and often ended, much to our surprise. Deep in the water Stalagmites also rose up in pinnacles and fringes through the water, which was so exquisitely still and clear that it was something difficult to tell where the solid marble tracery ended, and its reflected image began. In this cave, which is a considerable distance from the sea, there is a slight change of level with the tide sufficient [pg 113] to keep the water perfectly pure. The mouth of the cave is overgrown with foliage, and every tree is draped and festooned with the fragrant Jasminum gracile, mingled not unfrequently with the "poison ivy" (Rhus toxicodendron). The Bermudians, especially the dark people, have a most exaggerated horror of this bush. They imagine that if one touch it or rub against it he becomes feverish, and is covered with an eruption. This is no doubt entirely mythical. The plant is very poisonous, but the perfume of the flower is rather agreeable, and we constantly plucked and smelt it without its producing any unpleasant effect. The tide was with us when we regained the Flats Bridge, and the galley shot down the rapid like an arrow, the beds of scarlet sponges and the great lazy trepangs showing perfectly clearly on the bottom at a fathom depth.
Every here and there throughout the islands there are groups of bodies of very peculiar form projecting from the surface of the limestone where it has been weathered. These have usually been regarded as fossil palmetto stumps, the roots of trees which have been overwhelmed with sand and whose organic matter has been entirely removed and replaced by carbonate of lime. Fig. 1 represents one of the most characteristic [pg 114] of these from a group on the side of the road in Boaz Island. It is a cylinder a foot in diameter and six inches or so high; the upper surface forms a shallow depression an inch deep surrounded by a raised border; the bottom of the cup is even, and pitted over with small depressions like the marks of rain-drops on sand; the walls of the cylinder seem to end a few inches below the surface of the limestone in a rounded boss, and all over this there are round markings or little cylindrical projections like the origins of rootlets. The object certainly appears to agree even in every detail with a fossil palm-root, and as the palmetto is abundant on the islands and is constantly liable to be destroyed by and ultimately enveloped in a mass of moving sand, it seemed almost unreasonable to question its being one. Still something about the look of these things made me doubt, with General Nelson, whether they were fossil palms, or indeed whether they were of organic origin at all; and after carefully examining and [pg 115] pondering over several groups of them, at Boaz Island, on the shore at Mount Langton, and elsewhere, I finally came to the conclusion that they were not fossils, but something totally different.
The form given in Fig. 1 is the most characteristic, and probably by far the most common; but very frequently one of a group of these, one which is evidently essentially the same as the rest and formed in the same way, has an oval or an irregular shape (Figs. 2, 3, and 4). In these we have the same raised border, the same scars on the outside, the same origins of root-like fibres, and the same pitting of the bottom of the shallow cup; but their form precludes the possibility of their being tree-roots. In some cases (Fig. 5), a group of so-called "palm-stems" is inclosed in a space surrounded by a ridge, and on examining it closely this outer ridge is found to show the same leaf-scars and traces of rootlets as the "palm-stems" themselves. In some cases very irregular honey-combed figures are produced which the examination [pg 116] of a long series of intermediate forms shows to belong to the same category (Fig. 6).
In the caves in the limestone, owing to a thread of water having found its way in a particular direction through the porous stone of the roof, a drop falls age after age on one spot on the cave-floor, accurately directed by the stalactite which it is all the time creating. The water contains a certain proportion of carbonate of lime, which is deposited as stalagmite as the water evaporates, and thus a ring-like crust is produced at a little distance from the spot where the drop falls. When a ring is once formed, it limits the spread of the drop, and determines the position of the wall bounding the little pool made by the drop. The floor of the cave gradually rises by the accumulation of sand and travertine, and with it rise the walls and floor of the cup by the deposit of successive layers of stalagmite produced by the drop percolating into the limestone of the floor which hardens it still further, but in this peculiar symmetrical way. From the floor and sides of the cup the water oozes into the softer limestone around and beneath; but, as in all these limestones, it does not ooze indiscriminately, but follows certain more free paths. These become soon lined and finally blocked with [pg 117] stalagmite, and it is these tubes and threads of stalagmite which afterwards in the pseudo-fossil represent the diverging rootlets.
Sometimes when two or more drops fall from stalactites close to one another the cups coalesce (Figs. 2, 3, and 4); sometimes one drop or two is more frequent than the other, and then we have the form shown in Figs. 3 and 4; sometimes many drops irregularly scattered form a large pool with its raised border, and a few drops more frequent and more constant than the rest grow their "palmetto stems" within its limit (Fig. 5); and sometimes a number of drops near one another make a curious regular pattern, with the partitions between the recesses quite straight (Fig. 6).
I have already referred to the rapid denudation which is going on in these islands, and to the extent to which they have been denuded within comparatively recent times. The floors of caves, from their being cemented into a nearly homogeneous mass by stalagmitic matter, are much harder than the ordinary porous blown limestone; and it seems that in many cases, after the rocks forming the walls and roof have been removed, disintegration has been at all events temporarily arrested by the floor. Where there is a flat surface of rock exposed anywhere on the island, it very generally bears traces of having been at one time the floor of a cave; and as the weather-wearing of the surface goes on, the old concretionary structures are gradually brought out again, the parts specially hardened by a localized slow infiltration of lime resist integration longest and project above the general surface. Often [pg 118] a surface of weathered rock is so studded with these symmetrical concretions, that it is hard to believe that one is not looking at the calcified stumps of a close-growing grove of palms.
(From Studies Scientific and Social.) By
ALFRED RUSSEL WALLACE.
In the popular accounts of these trees it is usual to dwell only on the dimensions of the very largest known specimens, and sometimes even to exaggerate these. Even the smaller full-grown trees, however, are of grand dimensions, varying from fourteen to eighteen feet in diameter, at six feet above the ground, and keeping nearly the same thickness for perhaps a hundred feet. In the south Calaveras grove, where there are more than a thousand trees, the exquisite beauty of the trunks is well displayed by the numerous specimens in perfect health and vigor. The bark of these trees, seen at a little distance, is of a bright orange brown tint, delicately mottled with darker shades, and with a curious silky or plush-like gloss, which gives them a richness of color far beyond that of any other conifer. The tree which was cut down soon after the first discovery of the species, the [pg 120] stump of which is now covered with a pavilion, is twenty-five feet in diameter at six feet above the ground, but this is without the thick bark, which would bring it to twentyseven feet when alive. A considerable portion of this tree still lies where it fell, and at one hundred and thirty feet from the base I found it to be still twelve and a half feet in diameter (or fourteen feet with the bark), while at the extremity of the last piece remaining, two hundred and fifteen feet from its base, it is six feet in diameter, or at least seven feet with the bark. The height of this tree when it was cut down is not recorded, but as one of the living trees is more than three hundred and sixty feet high, it is probable that this giant was not much short of four hundred feet.
In the accompanying picture the dead tree in the centre is that from which the bark was stripped, which was erected in the Crystal Palace and unfortunately destroyed by fire. It is called the "Mother of the [pg 121] Forest." The two trees nearer the foreground are healthy, medium-sized trees, about fifteen feet diameter at six feet above the ground.
The huge decayed trunk called "Father of the Forest," which has fallen perhaps a century or more, exhibits the grandest dimensions of any known tree. By measuring its remains, and allowing for the probable thickness of the bark, it seems to have been about thirtyfive feet diameter near the ground, at ninety feet up fifteen feet, and even at a height of two hundred and seventy feet, it was nine feet in diameter. It is within the hollow trunk of this tree that a man on horse-back can ride—both man and horse being rather small; but the dimensions undoubtedly show that it was considerably larger than the "Pavilion tree," and that it carried its huge dimensions to a greater altitude; and although this does not prove it to have been much taller, yet it was in all probability more than four hundred feet in height.
Very absurd statements are made to visitors as to the antiquity of these trees, three or four thousand years being usually given as their age. This is founded on the fact that while many of the large Sequoias are greatly damaged by fire, the large pines and firs around them are quite uninjured. As many of these pines are assumed to be near a thousand years old, the epoch of the "great fire" is supposed to be earlier still, and as the Sequoias have not outgrown the fire-scars in all that time, they are supposed to have then arrived at their full growth. But the simple explanation of these trees alone having suffered so much from fire is, that their bark is unusually thick, dry, soft, and fibrous, [pg 122] and it thus catches fire more easily and burns more readily and for a longer time than that of the other coniferæ. Forest fires occur continually, and the visible damage done to these trees has probably all occurred in the present century. Professor C.B. Bradley, of the University of California, has carefully counted the rings of annual growth on the stump of the "Pavilion tree," and found them to be twelve hundred and forty; and after considering all that has been alleged as to the uncertainty of this mode of estimating [pg 123] the age of a tree, he believes that in the climate of California, in the zone of altitude where these trees grow, the seasons of growth and repose are so strongly marked that the number of annual rings gives an accurate result.
Other points that have been studied by Professor Bradley are, the reason why there are so few young trees in the groves, and what is the cause of the destruction of the old trees. To take the last point first, these noble trees seem to be singularly free from disease or from decay due to old age. All the trees that have been cut down are solid to the heart, and none of the standing trees show any indications of natural decay. The only apparent cause for their overthrow is the wind, and by noting the direction of a large number of fallen trees it is found that the great majority of them lie more or less towards the south. This is not the direction of the prevalent winds, but many of the tallest trees lean towards the south, owing to the increased growth of their topmost branches towards the sun. They are then acted upon by violent gales, which loosen their roots, and whatever the direction of the wind that finally overthrows them, they fall in the direction of the over-balancing top weight. The young trees grow spiry and perfectly upright, but as soon as they overtop the surrounding trees and get the full influence of the sun and wind, the highest branches grow out laterally, killing those beneath their shade, and thus a dome-shaped top is produced. Taking into consideration the health and vigor of the largest trees, it seems probable that, under favorable conditions of shelter from violent winds, and from a number of trees [pg 124] around them of nearly equal height, big trees might be produced far surpassing in height and bulk any that have yet been discovered. It is to be hoped that if any such are found to exist in the extensive groves of these trees to the south of those which are alone accessible to tourists, the Californian Government will take steps to reserve a considerable tract containing them, for the instruction and delight of future generations.
The scarcity of young Sequoias strikes every visitor, the fact being that they are only to be found in certain favored spots. These are, either where the loose débris of leaves and branches which covers the ground has been cleared away by fire, or on the spots where trees have been uprooted. Here the young trees grow in abundance, and serve to replace those that fall. The explanation of this is, that during the long summer drought the loose surface débris is so dried up that the roots of the seedling Sequoias perish before they can penetrate the earth beneath. They require to germinate on the soil itself, and this they are enabled to do when the earth is turned up by the fall of a tree, or where a fire has cleared off the débris. They also flourish under the shade of the huge fallen trunks in hollow places, where moisture is preserved throughout the summer. Most of the other conifers of these forests, especially the pines, have much larger seeds than the Sequoias, and the store of nourishment in these more bulky seeds enables the young plants to tide over the first summer's drought. It is clear, therefore, that there are no indications of natural decay in these forest giants. In every stage of their growth they are vigorous [pg 125] and healthy, and they have nothing to fear except from the destroying hand of man.
Destruction from this cause is, however, rapidly diminishing both the giant Sequoia and its near ally the noble redwood (Sequoia sempervirens), a tree which is more beautiful in foliage and in some other respects more remarkable than its brother species, while there is reason to believe that under favorable conditions it reaches an equally phenomenal size. It once covered almost all the coast ranges of central and northern California, but has been long since cleared away in the vicinity of San Francisco, and greatly diminished elsewhere. A grove is preserved for the benefit of tourists near Santa Cruz, the largest tree being two hundred and ninety-six feet high, twenty-nine feet diameter at the ground and fifteen feet at six feet above it. One of these trees having a triple trunk is here figured from a photograph. Much larger trees, however, exist in the great forests of this tree in the northern part of the State; but [pg 126] these are rapidly being destroyed for the timber, which is so good and durable as to be in great demand. Hence Californians have a saying that the redwood is too good a tree to live. On the mountains a few miles east of the Bay of San Francisco, there are a number of patches of young redwoods, indicating where large trees have been felled, it being a peculiarity of this tree that it sends up vigorous young plants from the roots of old ones immediately around the base. Hence in the forests these trees often stand in groups arranged nearly in a circle, thus marking out the size of the huge trunks of their parents. It is from this quality that the tree has been named sempervirens, or ever flourishing. Dr. Gibbons, of Alameda, who has explored all the remains of the redwood forests in the neighborhood of Oakland, kindly took me to see the old burnt-out stump of the largest tree he had discovered. It is situated about fifteen hundred feet above the sea, and is thirty-four feet in diameter at the ground. This is as large as the very largest specimens of the Sequoia gigantea, but it may have spread out more at the base and have been somewhat smaller above, though this is not a special characteristic of the species.
From The Atlantic Monthly, March, '93.) By
PROFESSOR E.S. HOLDEN.
I was once trying to tell a boy, a friend of mine, what the scientific men mean by the long word Evolution, and to give him some idea of the plan of the world. I wanted an illustration of something that had grown—evolved, developed—from small beginnings up through more and more complicated forms, till it had reached some very complete form. I could think of no better example than the railway by which we were sitting. The trains were running over the very track where a wagon-road had lately been, and before that a country cart-track, and before that a bridle-path, and before that again a mere trail for cattle. So I took the road for an example, and tried to show my boy how it had grown from little things by slow degrees according to laws; and if you like, I will try to tell it again.
Just as one can go further and further back, and always find a bird to be the parent of the egg, and an egg to be the parent of that bird, so in the history of [pg 128] this road of ours; we may go back and back into the past, always finding something earlier, which is the cause of the something later. The earth, the planets, and the sun were all a fiery mist long ago. And in that mist, and in what came before it, we may look for the origin of things as they are. But we must begin somewhere. Let us begin with the landscape as we see it now,— hills, valleys, streams, mountains, grass,—but with only a single tree.
We will not try to say how the tree came there. At least, we will not try just yet. When we are through with the story you can say just as well as I can.Suppose, then, a single oak-tree stood just on that hillside thousands and thousands of years ago. Grass was growing everywhere, and flowers, too. The seeds came with the winds. Year after year the oak-tree bore its acorns, hundreds and hundreds of them, and they fell on the grass beneath and rolled down the smooth slopes, and sprouted as best they could,—most of them uselessly so far as producing trees were concerned,—but each one did its duty and furnished its green sprout, and died if it found no nourishment.
All the hundreds of acorns rolled down the slopes, Not one rolled up; and here was a law,—the law of gravitation,—in full activity. There were scores of other laws active, too; for evolution had gone a long way when we had an earth fit to be lived on, and hills in their present shape, and a tree bearing acorns that would reproduce their kind. But ever since the fiery mist this simple law of gravitation has been acting, binding the whole universe together, making a relationship between each clod and every other clod, and [pg 129] forcing every stone, every acorn, and every rain-drop to move down and not up.
Just as this law operates,—continuously, silently, inexorably,—so every other law makes itself felt in its own sphere. Gravitation is simple. The law according to which an acorn makes an oak—and not a pine-tree is complex. But the laws of Nature are all alike, and if we understand the simple ones, we can at least partly comprehend the more complex. They are nothing but fixed habits on a large scale.
So the acorns fell year by year and sprouted; and one out of a thousand found good soil, and was not wasted, and made a tree. And so all around (below) the tree with which we started there grew a grove of oaks like it, in fact its children; and finally the original trees died, but not without having left successors.
First of all, the green hillside is smooth and untrodden. There is nothing but grass and flowers, borne there by the winds, which leave no track. There is no animal life even in this secluded spot save the birds, and they too leave no track. By and by there comes a hard winter, or a dearth of food, and a pair of stray squirrels emigrate from their home in the valley below; and the history of our hill and its woods begins. Mere chance decides the choice of the particular oak-tree in which the squirrels make their home. From the foot of this tree they make excursions here and there for their store of winter food,— acorns and the like,—and they leave little paths on the hillside from tree to tree.
The best-marked paths run to the places where there are the most acorns. A little later on there are more squirrels in the colony,—the young of the parent pair, [pg 130] and other colonists from the valley. The little tracks become plainer and plainer.
Later still come other wild animals in search of food,—squirrels will do. The wild animals do not remain in the colony (there are too few squirrels, and they are too hard to catch), but they pass through it, sometimes by day but oftenest by night.
You might think it was perfectly a matter of chance along which path a bear or a wolf passed, but it was not. He could walk anywhere on the hillside; and sometimes he would be found far out of the paths that the squirrels had begun. But usually, when he was in no haste, he took the easiest path. The easiest one was that which went between the bushes and not through them; along the hillside and not straight up it; around the big rocks and not over them. The wolves and bears and foxes have new and different wants when they come; and they break new paths to the springs where they drink, to the shade where they lie, to the hollow trees where the bees swarm and store the wild honey.
But the squirrels were the first surveyors of these tracks. The bears and wolves are the engineers, who change the early paths to suit their special convenience.By and by the Indian hunter comes to follow the wild game. He, too, takes the easiest trail, the path of least resistance; and he follows the track to the spring that the deer have made, and he drinks there. He is an animal as they are, and he satisfies his animal wants according to the same law that governs them.
After generations of hunters, Indians, and then white men, there comes a man on horseback looking for a [pg 131] house to live in. He, too, follows along the easiest paths and stops at the spring; and near by he finds the place he is looking for. Soon he returns, driving before him herds of cattle and flocks of sheep, which spread over the grassy glades to feed. But everywhere they take the easiest place, the old paths, from the shady tree to the flowing spring. After awhile the hillside is plainly marked with these sheep trails. You can see them now whenever you go into the country, on every hillside.
Soon there are neighbors who build their homes in the next valley, and a good path must be made between the different houses.A few days' work spent in moving the largest stones, in cutting down trees, and in levelling off a few steep slopes, makes a trail along which you can gallop your horse. Things move fast now,—history begins to be made quickly as soon as man takes a hand in it. Soon the trail is not enough: it must be widened so that a wagon-load of boards for a new house can be carried in (for the settler has found a wife). After the first cart-track is made to carry the boards and shingles in, a better road will be needed to haul firewood and grain out (for the wants of the new family have increased, and things must be bought in the neighboring village with money, and money can only be had by selling the products of the farm). By and by the neighborhood is so well inhabited that it is to the advantage of the villages all around it to have good and safe and easy roads there; and the road is declared a public one, and it is regularly kept in repair and improved at the public [pg 132] expense. Do not forget the squirrels of long ago. They were the projectors of this road. Their successors use it now,—men and squirrels alike,—and stop at the spring to drink, and under the huge oaks to rest.
A few years more, and it becomes to the advantage of all to have a railway through the valley and over the hillside. Then a young surveyor, just graduated from college, comes with his chain-men and flag-men, and finds that the squirrels, and bears, and hunters, and all the rest have picked out the easiest way for him long centuries ago. He makes his map, and soon the chief enigneer and the president of the road drive along in a buggy with a pair of fast horses (frightening the little squirrels off their road-way and into their holes), and the route of the Bear Valley and Quercus Railway is finally selected, and here it is. See! there comes a train along the track. This is the way a railway route grew out of a squirrel path. There are thousands of little steps, but you can trace them, or imagine them, as well as I can tell you.
It is the same all over the world. Stanley cut a track through the endless African forests. But it lay between the Pygmy villages, along the paths they had made, and through the glades where they fought their battles with the storks.
Sometimes the first road is a river—the track is already cut. Try to find out where the settlements in America were in the very early days—before 1800. You will find them along the Hudson, the Juanita, the St. Lawrence, the James, the Mississippi Rivers. But when these are left, men follow the squirrel-tracks and [pg 133] bear-tracks, or the paths of hunters, or the roads of Roman soldiers. It is a standing puzzle to little children why all the great rivers flow past the great towns. (Why do they?) The answer to that question will tell you why the great battles are fought in the same regions; why Egypt has been the coveted prize of a dozen different conquerors (it is the gateway of the East); why our Civil War turned on the possession of the Mississippi River. It is the roadways we fight for, the ways in and out, whether they be land or water. Of course, we really fought for something better than the mere possession of a roadway, but to get what we fought for we had to have the roadway first.
The great principle at the bottom of everything in Nature is that the fittest survives: or, as I think it is better to say it, in any particular conflict or struggle that thing survives which is the fittest to survive in this particular struggle. This is Mr. Darwin's discovery,—or one of them,—and the struggle for existence is a part of the great struggle of the whole universe, and the laws of it make up the methods of Evolution—of Development.
It is clear now, is it not, how the railway route is the direct descendant of the tiny squirrel track between two oaks? The process of development we call Evolution, and you can trace it all around you. Why are your skates shaped in a certain way? Why is your gun rifled? Why have soldiers two sets of (now) useless buttons on the skirts of their coats? (I will give you three guesses for this, and the hint that you must think of cavalry soldiers.) Why are eagles' wings of just the size that they are? These and millions [pg 134] of like questions are to be answered by referring to the principle of development.
Sometimes it is hard to find the clew. Sometimes the development has gone so far, and the final product has become so complex and special, that it takes a good deal of thinking to find out the real reasons. But they can be found, whether they relate to a fashion, to one of the laws of our country, or to the colors on a butterfly's wing.
There is a little piece of verse intended to be comic, which, on the contrary, is really serious and philosophical, if you understand it. Learn it by heart, and apply it to all kinds and conditions of things, and see if it does not help you to explain them to yourself....
"And Man grew a thumb for that he had need of it,A