great as now, or one degree for each three feet in depth (Geol. Journal, viii, 59.) The conclusion is inevitable that a condition of things must have existed during long periods in the history of the cooling globe, when the accumulation of comparatively thin layers of sediment would have been sufficient to give rise to all the phenomena of metamorphism, vulcanicity, and movements of the crust, whose origin Herschel has so well explained.

Coming, in the next place, to consider the influence of pressure upon the buried materials derived from the mechanical and chemical disintegration of the primitive crust, we find that by the presence of heated water throughout them, they are placed under conditions very unlike those of the original cooling mass. While pressure raises the fusing point of such bodies as expand in passing into the liquid state, it depresses that point for those which, like ice, contract in becoming liquid. The same principle extends to that liquefaction which constitutes solution; where, as is with few exceptions the case, the process is attended with condensation or diminution of volume, pressure will, as shown by the experiments of Sorby, augment the solvent power of the liquid. Under the influence of the elevated temperature and the great pressure which prevail at considerable depths, sediments should, therefore, by the effect of the water which they contain, acquire a certain degree of liquidity, rendering not improbable the suggestion of Scheerer, that the presence of five or ten per cent of water may suffice, at temperatures approaching redness, to give to a granitic mass a liquidity partaking at once of the character of an igneous and an aqueous fusion. The studies by Mr. Sorby of the cavities in crystals have led him to conclude that the constituents of granitic and trachytic rocks have crystallized in the presence of liquid water, under great pressure, at temperatures not above redness, and consequently very far below that required for simple igneous fusion. The intervention of water in giving liquidity to lavas, has, in fact, long been taught by Scrope, and notwithstanding the opposition of Plutonists, like Durocher, Fournet, and Rivière, is now very generally admitted. In this connection, the reader is referred to the Geological Magazine for February, 1868, page 57, where the history of this question is discussed.

It may here be remarked that if we regard the liquefaction of heated rocks under great pressure, and in presence of water, as a process of solution rather than of fusion, it would follow that diminution of pressure, as supposed by Mr. Scrope, would cause, not liquefaction, but the reverse. The mechanical pressure of great accumulations of sediment is to be regarded as cooperating with heat to augment the solvent action of the water, * Sorby, Bakerian Lecture, Royal Society, 1863.

and as being thus one of the efficient causes of the liquefaction. of deeply buried sedimentary rocks.

As

[The following extracts from a note by the author to the Geological Magazine for February 1870, may be cited in further elucidation of this point:-"pressure, which in the first case, that of simple fusion of anhydrous materials, prevents liquefaction by preventing expansion, in the second case (that of igneoaqueous fusion or liquefaction at high temperatures, by the aid of a small portion of water, as maintained by Scrope, Scheerer and Elie de Beaumont) on the contrary, favors liquefaction by promoting the solution of the water-impregnated mass. Sorby has shown, a conversion of mechanical into chemical force appears in the increase of solubility under pressure. In other words, pressure prevents fusion when, as in most instances, it is a process of expansion, but favors solution, which is, with few exceptions, a process of contraction. Now since Í place the seat of volcanic action in a region where solution, rather than simple fusion, is the cause of liquidity, I am led to consider pressure as one of the efficient causes of the liquefaction of rocks, and to regard its diminution as leading to solidification."]*

That the water intervenes not only in the phenomena of volcanic eruptions, but in the crystallization of the minerals of eruptive rocks, which have been formed at temperatures far below that of igneous fusion, is a fact not easily reconciled with either the first or the second hypothesis of volcanic action, but is in perfect accordance with the one here maintained, which is also strongly supported by the study of the chemical composition of igneous rocks. These are generally referred to two great divisions, corresponding to what have been designated the trachytic and pyroxenic types, and to account for their origin, a separation of a liquid igneous mass beneath the earth's crust into two layers of acid and basic silicates, was imagined by Philips, Durocher, and Bunsen. The last mentioned, as is well known, has calculated the normal composition of these supposed trachytic and pyroxenic magmas, and conceives that from them, either separately, or by admixture, the various eruptive rocks are derived; so that the amounts of alumina, lime, magnesia and alkalies, sustain a constant relation to the silica in the rock. If, however, we examine the analyses of the eruptive rocks in Hungary and Armenia, made by Streng, and put forward in support of this view, there will be found such discrepancies between the actual and the calculated results as to throw grave doubts on Bunsen's hypothesis.

*See in this connection, Mr. Scrope on “The Character of Lavas," in the Geological Magazine for March 1870.

Two things become apparent from a study of the chemical nature of eruptive rocks; first, that their composition presents such variations as are irreconcilable with the simple origin generally assigned to them, and second, that it is similar to that of sedimentary rocks, whose history and origin it is, in most cases, not difficult to trace. I have elsewhere pointed out how the natural operation of mechanical and chemical agencies tends to produce among sediments, a separation into two classes, corresponding to the two great divisions above noticed. From the mode of their accumulation, however, great variations must exist in the composition of the sediments, corresponding to many of the varieties presented by eruptive rocks. The careful study of stratified rocks of aqueous origin discloses, in addition to these, the existence of deposits of basic silicates of peculiar types. Some of these are in great part magnesian, others consist of compounds like anorthite and labradorite, highly aluminous basic silicates, in which lime and soda enter, to the almost complete exclusion of magnesia and other bases; while in the masses of pinite or agalmatolite rock we have a similar aluminous silicate, in which lime and magnesia are wanting, and potash is the predominant alkali. In such sediments as these just enumerated we find the representatives of eruptive rocks like peridotite, phonolite, leucitophyre, and similar rocks, which are so many exceptions in the basic group of Bunsen. As, however, they are represented in the sediments of the earth's crust, their appearance as exotic rocks, consequent upon a softening and extravasation of the more easily liquefiable strata of deeply buried formations, is readily and simply explained.*

The object of the present communication has been to call the attention of geologists to the neglected views of Keferstein and Herschel, which I have endeavored to extend--and to adapt to the present state of our knowledge. It is proposed in another paper to consider the question of the agencies which have regulated the geographical distribution of volcanic phenomena both in ancient and in modern times.

Montreal, Canada, March, 1869.

* See in this connection the Canadian Journal for 1858, p. 203; Quart. Jour. Geol. Society for 1859, p. 494; this Jour., II, xxxvii. 255, xxxviii, 182; also Geology of Canada, 1863, pp. 643, 669, and Rep. Geol. Canada, 1866, p. 230.

ART. IV.-Notes on some features of the Flora of Eastern Kansas; by ELIHU HALL.

[The following consists of two articles (somewhat curtailed) published in the Prairie Farmer, which give so clear an exposition of the general features of the vegetation of the region under consideration, that we have sought and obtained permission to reproduce them in this Journal.-EDS.]

TREE GROWTH.-In a trip in September last in a wagon through a portion of Eastern Kansas, from Forts Scott and Humboldt north to Leavenworth and Atchison, I had excellent opportunities for observation of its general flora, and more especially so that of the autumnal months. The general character of its arborescent flora is decidedly adverse to a favorable impression of the adaptation of the country to tree growth. The question arises why all these dwarfed, distorted, abnormally developed specimens everywhere, as compared with the true type of trees, such as we are accustomed to in our own noble denizens of the Mississippi Valley forests. True, on the larger streams, the black alluvial deposit grow some very fine specimens of black walnut, cottonwood and elms, but this area is quite limited.

In

We should naturally infer from this character of the native arborescent growth of the country that causes had been long existing and were yet in operation to produce so general a result; but since the settlement or since the planting of trees has been commenced there by the inhabitants, everywhere living evidences are springing up directly opposing all such inferences. some parts of Jefferson county, artificial groves only ten years old, are already 50 feet high, and appearing, through the misty haze of autumn, like natural groves on the prairies of central Illinois. There are evidences, too, that the native growth, that is, the young trees, in all the bushy regions, are making good speed in becoming saplings of proper proportions; this is particularly so of the hickory, (Carya alba and C. porcina.)

These many facts satisfy us that the causes of the abnormal tree growth here are not ascribable to an uncongenial climate, nor to aridity or sterility of soil, nor to exposure, for the flourishing artificial groves in Jefferson county are upon as high land as there is probably in the state, so near the Missouri river. The growth of fruit trees, apple, peach, pear, and the grape vine, during the past season, has been prodigious.

SPECIES AND DISTRIBUTION OF NATIVE TREES.-The Oak Family is represented by Quercus obtusiloba everywhere in the bushy regions, principally as dwarfed low trees and bushes.

Q. macrocarpa is less abundant, but occurs throughout, some specimens of fair proportions. Q. Prinus, (var. humilis,) every

where in the bushy regions from one foot to forty feet high, fruiting abundantly; the very smallest bushes. The White Oak (Q. alba) was not met with. I doubt if there is a specimen in the State, authors of books on Kansas and travelers to the contrary notwithstanding. It is known to be one of the first oaks that fails westward, and probably does not reach the State at any point.

Quercus coccinea was frequently met with, but is not abundant; all dwarfed specimens.

Quercus rubra is more plentiful, principally young trees.

Quercus palustris, in the southern portion of the State is abundant, the principal tree-growth mostly bushes and young trees, and some large old specimens of fair proportions on the bottoms of the larger streams.

The Hickory Family is represented by Juglans nigra, on the streams, but not plentiful; a few large specimens.

Carya alba, C. sulcata, C. porcina, C. amara and C. olivaformis, (the Pecan ;) the latter abounds abundantly in the southern part of the State, but so far as seen, in bushy specimens or young trees of little promise. Carya alba and C. porcina are the two species springing up thickly in the bushy regions, and are destined soon to afford an abundance of the best of fuel; are already of size for hoop-poles in many places northward. Ulmus fulva and Ulmus Americana abound on the streams. These are the two commonest elms everywhere westward; the latter principally prevailing.

Populus monilifera, the common cotton-wood, was frequently met with, but is probably not plenty after leaving the Missouri river. Neither of the Aspens, so common in the regions further north, was seen. The maples are rare trees. Acer sacharinum was not seen. A few well grown trees of Negundo aceroides, (the box elder). The Diospyros Virginiana, (Persimmon,) is an abundant shrub southward, and the Pawpaw (Asimina triloba) is scarcely less common in that region.

THE HERBACEOUS FLORA, as would be expected, partakes much of the character of the high plain flora west of the Missouri river; the country being chiefly prairie: the number of species is small, but individuals aggregate immensely. Of the grasses, Andropogon furcatus, A. scoparius and Sorghum nutans, compose probably 80 per cent. These are the chief hay grasses, and probably the most used by grazing stock in the summer; but the winter forage plant, as I learned from the inhabitants, the one upon which their cattle graze and fatten during the winter months, and from which Kansas has gained her reputation as a country where stock needed feeding a few weeks in the year, is Sporobolus heterolepis. This grass only abounds plentifully in certain localities; it affects the moister and flatter portions of the prairie, and is most common southward. It is a