There's nought around us that doth cease to be.
Each object varies but in form and hue,
Its parts exchange; hence combinations new.
And thus is Nature through her mighty frame
For ever varying, and yet still the same."
In the world of life we see how animals are sustained by a constant series of chemical changes in their blood, every respiration of air adding, as it were, fresh fuel to the flame of life within. In plants, too, there is an analogous process. The atmospheric air is by them decomposed, part of it being given off again, and part retained to build up the organic structure. Plants withdraw mineral matter from the soil, animals feed upon plants, and thus the earthy substances, after having formed a part, first of rock masses, then of vegetable, and subsequently of animal organizations, are returned again to the soil, whence to be once more withdrawn and undergo new cycles of mutation. But this perpetual interchange is not confined to the vital world. We see it in the action of winds, when heated air rises and moves in one direction, and the colder parts sink and travel the opposite way. The same principle is exhibited by the oceanic currents, the removal of a body of water, from whatever cause, always necessitating the ingress of a corresponding quantity to supply its place. But perhaps one of the most beautiful instances of these interchanges in the whole inorganic world is the ceaseless passage of water from the land to the sea, and from the sea to the land. The countless thousands of rivulets, and streams, and gigantic rivers, that are ever pouring their waters into the great deep, do not in the least raise its level or diminish its saltness. And why? Simply because the sea gives off by evaporation as much water as it receives from rain and rivers. The vapour thus exhaled ascends to the upper regions of the atmosphere, where it forms clouds, and whence it eventually descends as rain. The larger part of the rain probably falls upon the ocean, but a considerable amount is nevertheless driven by winds across the land. This finds its way into the streams, and so back again to the sea, only, however, to be anew evaporated and sent as drizzling rain across the face of land and sea. This interchange is constantly in progress, and seems to have been as unvarying during past ages.
But the ceaseless passage of water between land and sea is not a mere isolated and independent phenomenon. Like all the rest of Nature's processes, even the simplest, it produces important and complicated effects. And the reader may, perhaps, think it worth looking at for a little, when he reflects that to this seemingly feeble cause we owe no small part of our solid lands, whether as islands wasted by the sea, or as part of vast and variegated continents, wide rolling prairies covered with verdure and roamed over by herds of cattle, or wintry Alpine hills lifeless and bare.
The truth of this will appear when we reflect that the moisture which rises from the sea and falls on the land as rain, is free from any admixture of impurities; but by the time it again reaches the sea, after a circuit of perhaps many miles down valley and plain, it has grown turbid and discoloured, carrying with it a quantity of mud, sand, and drift-wood. The sediment thus transported soon sinks to the bottom, where it eventually hardens into rock, and in course of time is raised above the waves as part of a new land. Such I conceive to have been the origin of the sand, gravel, and imbedded plants of our boulder. It may be well, however, in going into the details of the subject, to take a wider view of this interesting branch of geology, and look for a little at the forms and modes of the decomposition of rocks, and the varied manner in which new sedimentary accumulations are formed.
All over the world, wherever a land surface spreads out beneath the sky, there goes on a process of degradation and decay. Hills are insensibly crumbling into the valleys, valleys are silently eroded, and crags that ever since the birth of man have been the landmarks of the race, are yet slowly but surely melting away. It matters not where the hill or plain may lie, the highest mountains of the tropics and the frozen soil of the poles, yield each in its measure and degree to the influence of the general law. It might seem that so universal a process should be the result of some equally prevalent and simple cause. But when we set ourselves to examine the matter, we find it far otherwise. The waste of the solid lands, in place of arising from some single general action, is found to result from a multiform chain of causes, often local in their operation and variable in their effects. Such an investigation affords a good illustration of the general mode and fashion in which Nature delights to work. It shows us that what may seem a very simple process may be in reality a very complicated one; that in truth there exist in the world around us few if any simple, single processes, which stand out by themselves unconnected with any other; that, on the contrary, all become intimately linked together, the effects of one often forming part of the chain of causes in another, and producing by their combined action that complex yet strikingly harmonious order that pervades all the operations of Nature. To an extent of which Cicero never dreamed, there runs through all the world "such an admirable succession of things that each seems entwined with the other, and all are thus intimately linked and bound together."[51] Man separates out these various processes, classifies and arranges them, because from the imperfection of his mental powers he cannot otherwise understand their effects; all would seem but chaos and confusion. But the formal precision and the sharp lines of demarcation exist only in his mind. They have no place in the outer world. There we see process dove-tailing with process, and spreading out over the material world in an endless network of cause and effect. We feebly try to trace out these interlacing threads, but we can follow them far in no direction. Proteus-like, they seem to change their aspect, blending now into one form, now into another, and so eluding our keenest pursuit.
[51] Cicero, De Nat. Deor. lib. i. 4. So, in Bacon's Wisdom of the Ancients, under the fable "Pan or Nature:"—"The chain of natural causes links together the rise, duration, and corruption; the exaltation, degeneration, and workings; the processes, the effects, and changes, of all that can any way happen to things." Such is the philosopher's explanation of the Destinies as sisters of Pan. In no part of his writings can the thorough practical character of Bacon's philosophy be more conspicuously seen than in his treatment of these ancient fables. Glancing over the titles of the different papers, you are tempted to wonder what an intellect which could only appreciate poetry as a mode of narrating history or as a vehicle for the teaching of truth, will make of such fairy tales as those of Pan, Orpheus, Proteus, Cupid, and many others. They seem like so many airy Naiads crushed within the iron grasp of a hundred-banded Briareus. But a perusal of those delightful pages will show that the giant has really no malevolent intentions towards his fair prisoners; nay, that he only wishes, by stripping them of their paint and finery, to show that, with all their lightness and grace, they are nevertheless strong buxom dames, of the same doughty race with himself.