we have no reason to suppose that they mark the commencement of sedimentary deposits; they were doubtlessly derived from the ruins of other rocks in which the proportion of soda was still greater; and the detritus of these Laurentian felspars, making up our palæozoic strata, is now the source of alkaline waters by which the soda of the silicates, rendered soluble, is carried down to the sea in the form of carbonate to be transformed into chlorid of sodium. The lime of the feldspars being at the same time removed as carbonate, these sedimentary strata in the course of ages become less basic, poorer in soda and lime, and comparatively richer in alumina, silica, and potash. Hence in more recent crystalline rocks we find a less extensive development of soda-feldspars, while orthoclase and mica, chlorite and epidote, and silicates of alumina, like chiastolite, kyanite, and staurotide, which contain but little or no alkali, and are rare in the older rocks, become abundant.

The decomposition of the rocks is more slow now than formerly, because soda-silicates are less abundant, and because the proportion of carbonic acid in the air (an efficient agent in these changes,) has been diminished by the formation of limestones and coal. It will be evident that the principles above laid down are only applicable to the study of rocks in great masses, and refer to the predominance of certain mineral species at certain geologic epochs, since local and exceptional causes may reproduce in different epochs the conditions which belong to other periods.

VII. Mr. Babbages has shown that the horizons or surfaces of equal temperature in the earth's crust must rise and fall, as a consequence of the accumulation of sediment in some parts and its removal from others, producing thereby expansion and contraction in the materials of the crust, and thus giving rise to gradual and wide-spread vertical movements. Sir John Herschel|| subsequently showed that, as a result of the internal heat thus retained by accumulated strata, sediments deeply enough buried will become crystallized and ultimately raised, with their included water, to the melting point. From the chemical reactions at this elevated temperature, gases and vapours will be evolved, and earthquakes and volcanic eruptions will result. At the same time the disturbance of the equilibrium of pressure consequent upon the transfer of sediments, while the yielding surface reposes upon a mass of matter partly liquid and partly solid, will enable us to explain the phenomena of elevation and subsidence.

§ "On the Temple of Serapis." Proc. Geol. Soc., vol. ii, p. 73. Ibid. vol. ii, pp. 548 & 596.

According, then, to Sir J. Herschel's view, all volcanic phenomena have their source in sedimentary deposits; and this ingenious hypothesis, which is a necessary consequence of a high central temperature, explains in a most satisfactory manner the dynamical phenomena of volcanoes, and many other obscure points in their history, as for instance, the independent action of adjacent volcanic vents, and the varying nature of their ejected products. Not only are the lavas of different volcanoes very unlike, but those of the same crater vary at different times; the same is true of the gaseous matters, hydrochloric, hydrosulphuric, and carbonic acids. As the ascending heat penetrates saliferous strata, we shall have hydrochloric acid, from the decomposition of sea-salt by silica in the presence of water; while gypsum and other sulphates, by a similar reaction, would lose their sulphur in the form of sulphurous acid and oxygen. The intervention of organic matters, either by direct contact, or by giving rise to reducing gases, would convert the sulphates into sulphurets, which would yield sulphuretted hydrogen when decomposed by water and silica or carbonic acid, the latter being the result of the action of silica upon earthy carbonates. We conceive the ammonia so often found among the products of volcanoes to be evolved from the heated strata, where it exists in part as ready-formed ammonia (which is absorbed from air and water, and pertinaciously retained by argillaceous sediments), and is in part formed by the action of heat upon azotized organic matter present in these strata, as already maintained by Bischof.* Nor can we hesitate to accept this author's theory of the formation of boracic acid from the decomposition of borates by heat and aqueous vapour.†

The almost constant presence of remains of infusorial animals in volcanic products, as observed by Ehrenberg, is evidence of the interposition of fossiliferous rocks in volcanic phenomena.

The metamorphism of sediments in situ, their displacement in a pasty condition from igneo-aqueous fusion as plutonic rocks, and their ejection as lavas with attendant gases and vapours are, then, all results of the same cause, and depend upon the differences in the chemical composition of the sediments, the temperature, and the depth to which they are buried: while the unstratified nucleus of the earth, which is doubtless anhydrous, and according to the calculations of Messrs. Hopkins and Hennessey, probably solid to a great Lehrbuch der Geologie, vol. ii, pp. 115-122. Ibid. vol i, p. 669.

depth, intervenes in the phenomena under consideration only as a source of heat.

VIII. The volcanic phenomena of the present day appear, so far as I am aware, to be confined to regions covered by the more recent secondary and tertiary deposits, which we may suppose the central heat to be still penetrating (as shown by Mr. Babbage), a process which has long since ceased in the paleozoic regions. Both normal metamorphism and volcanic action are generally connected with elevations and foldings of the earth's crust, all of which pheenomena we conceive to have a common cause, and to depend upon the accumulation of sediments and the subsidence consequent thereon, as maintained by Mr. James Hall in his theory of mountains. The mechanical deposits of great thickness are made up of coarse and heavy sediments, and by their alteration yield hard and resisting rocks; so that subsequent elevation and denudation will expose these contorted and altered strata in the form of mountain-chains. Thus the Appalachians of North America mark the direction and extent of the great accumulation of sediments by the oceanic cur

[The notion that volcanic phenomena have their seat in the sedimentary formations of the earth's crust, and are dependant upon the combustion of organic matters, is as Humboldt remarks, one which belongs to the infancy of geognosy (Cosmos, vol. v, p. 443. Otte's translation). In 1834 Christian Keferstein published his Naturgeschichte des Erdkörpers, in which he maintains that all crystalline non-stratified rocks, from granite to lava, are products of the transformation of sedimentary strata, in part very recent, and that there is no well-defined line to be drawn between neptunian and volcanic rocks, since they pass into each other. Volcanic phenomena according to him have their origin, not in an igneous fluid centre, nor an oxydizing metallic nucleus, but in known sedimentary formations, where they are the result of a peculiar process of fermentation, which crystallizes and arranges in new forms the elements of the sedimentary strata, with evolution of heat as an accompaniment of the chemical process. (Naturgeschichte, vol. 1 p. 109, also Bull. Soc. Géol. de France (1) vol. vii. p. 197.)

These remarkable conclusious were unknown to me at the time of writing this paper, and seem indeed to have been entirely overlooked by geological writers; they are, as will be seen, in many respects an anticipation of the views of Herschel aud my own; although in rejecting the influence of an incandescent nucleus as a source of heat, he has, as I conceive, excluded the exciting cause of that chemical change, which he has not inaptly described as a process of fermentation, and which is the source of all volcanic and plutonic phenomena. See in this connection my paper on the Theory of Igneous Rocks and Volcanoes, in the Canadian Journal for May, 1858.]

rents during the whole paleozoic period; and the upper portions of these having been removed by subsequent denudation, we find the inferior members of the series transformed into crystalline stratified rocks.§

[§ The theory that volcanic mountains have been formed by a sudden local elevation or tumefaction of previously horizontal deposits of lava and other volcanic rocks, in opposition to the view of the older geologists who supposed them to have been built up by the accumulation of successive eruptions, although supported by Humboldt, Von Buch, and Elie de Beaumont, has been from the first opposed by Cordier, Constant Prevost, Scrope and Lyell. (See Scrope, Geol. Journal, vol. xii, p. 326, and vol. xv. p. 500; also Lyell, Philos. Trans. part 2, vol. cxlviii, p. 703, for 1858.) In these will we think be found a thorough refutation of the elevation hypothesis and a vindication of the ancient theory.

This notion of paroxysmal upheaval once admitted for volcanoes was next applied to mountains which, like the Alps and Pyrenees, are composed of neptunian strata. Against this view, however, we find De Montlosier in 1832 maintaining that such mountains are to be regarded as the remnants of former continents which have been cut away by denudation, and that the inversions and disturbances often met with in the structure of mountains are to be regarded only as local accidents. (Bul Soc. Geol., (1) vol. ii, p. 438, vol. iii, p. 215.)

Similar views were developed by Prof. James Hall in his address before the American Association for the Advancement of Science, at Montreal in August 1857. This address has not been published, but they are reproduced in the first volume of his Report on the Geology of Iowa, p. 41. He there insists upon the conditions which in the ancient seas gave rise to great accumulations of sediment along certain lines, and asserts that to this great thickness of strata, whether horizontal or inclined, we are to ascribe the mountainous features of North Eastern America as compared with the Mississippi valley. Mountain heights are due to original depositions and subsequent continental elevation, and not to local upheaval or foldings, which on the contrary, give rise to lines of weakness, and favor erosion, so that the lower rocks become exposed in anticlinal valleys, while the intermediate mountains are found to be capped with newer strata.

In like manner J. P. Lesley asserts that "mountains are but fragments of the upper layers of the earth's crust," lying in synclinals and preserved from the general denudation and translation. (Iron Manufacturer's Guide, 1859, p. 53.]

ARTICLE XXXIV.-Fossils of the Chazy Limestone, with de scriptions of new species. By E. BILLINGS.

(Extracted from the Report of the Geological Survey of Canada for 1858-59.)

The following paper contains an enumeration of the species of organic remains known to occur in the Chazy formation in Canada, so far as they can be ascertained from the collections made, up to the present date. The total number of species is 129, and they may be distributed as follows:—

The species which pass upwards into the overlying formations are Stenopora fibrosa, Lingula Huronensis, Strophomena alternata, S. incrassata, Orthis disparalis, O. perveta, O. subæquata, 0. gibbosa, O. borealis, Ctenodonta nasuta, Helicotoma umbili cata, Murchisonia perangulata, Maclurea Logani, M. Magna, Orthoceras multicameratum, O. bilineatum, O. Allumettense, O. Minganense, Illanus arcturus, Asaphus platycephalus (?), Leperditia fabulites (Conrad), var. (nana), Jones.

The genera, with the exception of some of those of the Cystideæ and Crinoideæ, all pass upwards into the more recent formations. The genus Amphion has not been found in any higher rocks in Canada; but I think I have read an account somewhere of its occurrence in the blue limestone of the Western States. The genera of Cystidea, which thus far we find peculiar to the Chazy, are Malocystites and Palæocystites. Glyptocystites passes upwards into the Trenton, and I have also seen fragments of what I think a species of Pleurocystites in the Chazy. Of the crinoidal genera,