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constant but much longer working of the ordinary forces.1

The names Neptunists and Plutonists, or Vulcanists, denote another deeply-rooted opposition of parties; this depends on the relative influence which is accorded to water and to fire respectively in the formation of the earth.

Water and fire are still active agents in forming and transforming the crust of the earth. The agency of fire shows itself principally in the volcanoes, which cause mountains and islands to rise, cast forth lava, ashes, and other substances; and possibly are the principal causes of earthquakes, and of all their effects on the earth's crust. The agency of water is twofold, chemical and mechanical. From substances which have been chemically dissolved in water are formed precipitations, tufaceous limestone, silicious sinter, stalactites, travertine marble, etc., and solid substances are carried by water, especially by rivers, from place to place, and then deposited. The deltas at the mouths of the Nile, the Ganges, the Rhine, and other rivers were formed in this way; it has been estimated that the Ganges and the Mississippi, for example, carry down yearly several thousand million cubic feet of solid substances, either floating in the water or in a state of solution.

1 Cf. Hæckel, Nat. Schöpfungsgeschichte, p. 101; and "Die Entstehung der Erdoberflache," in Burmeister's Geol. Bildern, i. p. 1. "The earth, and especially the earth's surface, has been entirely produced (!) by forces which we ourselves still find acting with similar power; it has never been subjected to more violent, or to any other kind of catastrophes of development. On the other hand, the period of time in which the development took place is quite immeasurable; there is nothing prodigious, nothing marvellous in the course of the earth's development, except the immense duration of time." P. 12.

As it appears from these and other facts that water and fire are at present active agents in transforming the surface of the earth, we are justified in assuming that they acted analogously in earlier times. If we go beyond the surface, and investigate the earth's crust, we find throughout, superposed one on another, a series of strata, or of stratified formations,' which it is universally supposed were formed by the gradual deposit of water. As a rule they consist of substances which are not soluble in water, and they certainly have all the qualities which we now find in newly formed watery deposits or sediments. Further, many of them contain petrifactions, that is, remains of organic bodies; now organic substances are not fireproof; therefore the strata which contain petrifactions can never have been in a state of igneous fusion, but can only have been dissolved by being mingled with water. All stratified formations which contain petrifactions are therefore supposed by geologists, Plutonists as well as Neptunists, to have a Neptunian origin.

But the crust of the earth does not consist entirely of stratified rocks; a great part of it is of different formation. These unstratified rocks are not found in parallel layers, but they occur without regularity in their stratification and succession, under, among, and above the stratified rocks; they consist of several mixed, completely or incompletely crystallized minerals; they are occasionally rich in precious stones and all

1 A formation, sometimes called system, by the French " terrain," is a collection of rocks which, either through age, origin, or composition, have a common character. Thus we speak of stratified and unstratified, Plutonic and Neptunian, soft water and sea water, metalliferous and non-metalliferous formations.

kinds of metals, but they are without petrifactions. Some of these unstratified rocks, as, e.g., true basalt, are generally acknowledged to have a volcanic origin. But when we come to the great mass of the unstratified rocks, consisting of granite, porphyry, serpentine marble, gneiss, mica slate, etc., the contest between Neptunism and Plutonism begins. The Plutonists assume that these rocks were formerly in a state of igneous fusion. Further, they think they may assume that the interior of the earth is still in a condition of igneous fusion. They found this assumption on the fact that heat increases as we penetrate deeper into the interior of the earth; and further, on the existence of hot springs, and especially of volcanoes, which, according to this theory, are open chimneys connected with the fluid nucleus of the earth. If this theory is admitted to be true so far, it is only logical to assume further that the whole earth was formerly a molten mass of igneous fluid, and from this condition passed by degrees into a solid state through the gradual cooling of its surface. While the earth was cooling, the outermost layer congealed first and formed a solid crust, on which water could gather, and the different stratified systems could by degrees be deposited. The irregularities of the earth's crust, the mountains and valleys, the seas and continents, were caused by the rebellion of the igneous fluid against the increasing mass of strata on the crust; for the outer strata were puffed out, vaulted, rent, dislocated, and occasionally overturned by upheavals, which were caused by the vapours enclosed in the interior. In many places the 1 1 Pfaff, Schöpfungsgeschichte, p. 208.

upheaving masses came to light, and appcar in the shape of crystalline rocks, showing their primitive form principally in granite. In other places the convulsion was not great enough to cause the upheaving masses to appear, and here only the lower strata are seen in a more or less vaulted shape. In other places again the fiery masses penetrated into splits and cracks in the stratified formations, and are there found as crystalline rocks. Sometimes the fiery masses and the vapours which caused their upheaval transformed the stratified formations with which they came in contact. In this manner the fiery masses in the interior of the earth acted in ancient days on the formation of the earth's crust; and the present volcanic outbreaks are feeble successors of those ebullitions of force which must have been much mightier and more extended in former times.

This, the Plutonic theory, was defended by Hutton (1726-1797) and by the great German geologist Leopold von Buch; and judging from the most recent handbooks of geology, it may be regarded as the one most generally recognised. As you see, even according to this theory, the authority is divided between Pluto and Neptune; but fire was the first and most mighty agent in the formation of the earth. Water formed and moulded the crust of the earth, but the deeper we penetrate into the earth, and the farther we go back in its history, the more do we find fire as the active agent.

I now come to the second theory, the Neptunian. This does not assert that fire had no part in the formation of the earth's crust; the volcanic phenomena which we still witness would of course not permit of this.

The basaltic rocks, for instance, are regarded by Neptunists as in great part volcanic masses which have sprung forth from the depths of the earth. But in this theory it is supposed that volcanoes are local phenomena, fed by fire which exists in certain places at no great depth, whose outbreaks are conditioned by chemical reactions. According to this view, the earth has no igneous core. Further, it is assumed that the earth never existed in a condition of igneous fusion, but was dissolved in water, or was partly just solid, partly fluid or dissolved, which condition was produced by water. This primæval broth (Ur-brei) gradually assumed a solid form through mechanical forces, pressure, etc., and still more through chemical processes, and by degrees the separate mountain ranges appeared. Most of the rocks which, according to the first theory, were originally in a state of igneous fusion, and in this condition were pressed up from below, according to this theory, were originally watery deposits and sediments, which gradually reached their present condition through chemical changes, metamorphoses and crystallization. Granite, porphyry, and the greenstones were thus formed. The numerous phenomena which, in the first theory, are regarded as the effects of volcanic agency, and of the rebellion of the igneous core against the hard crust of the earth, are here supposed to be the results of this chemical transformation, and of the continual dissolving and crystallization which are going on in the interior of the stratified rocks. The cause of earthquakes, for instance, may often be this: the limestone and other strata in the interior of the earth which are soluble in water, may be washed away and gradually

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