and possibly also the form of Cyclopteris represented by C. Jacksoni, which differs from any fern of the coal formation, and is perhaps entitled as Lesquereux maintains to a distinct generic name. The generic assemblage in the beds now under consideration, resembles that in the lower coal formation, and differs from that in the true coal measures, in the prevalence of Lycopodiaceus plants and the comparative absence of Sigillariæ; but the genera Lepidodendron and Sagenaria so characteristic of the lower coal measures are slenderly represented here. It is also to be observed that the genera Asterophyllites and Sphenophyllum, though common to the St. John group and the coal measures, are, in so far as known, absent from the lower coal formation in Nova Scotia and New Brunswick. The former genus is however found in the Lower coal in Silesia. It is interesting to observe in the St. John beds which have been disturbed and metamorphosed befare the carboniferous period, a generic assemblage so similar to that of the coal. On the other hand it is still more curious to find that the absence of the great Sigillaroid and Ulodendroid trees, so characteristic of the wide swampy flats of the coal period, gives to the St. John flora a more modern aspect than that of the coal; though in its exclusively cryptogamous and gymnospermous character, and in its generic forms, it is quite as decidedly palæozoic. In comparing the plants in the Devonian of Eastern America with those of Europe, a smaller proportion of identical species appears than in the case of the coal measures. There may have been in the Devonian period a greater geographical separation or climatic difference between the European and American land than in the time of the coal formation. On the other hand, however, a part of the plants ascertained here belong to the Lower Devonian, which has hitherto afforded only one land species in Europe, while here it contains several well preserved species and even a small bed of coal; and with respect to the Upper Devonian the number of known species is too small as yet to admit of a satisfactory comparison. I trust that the species described in this and my previous paper are but a small instalment of those to be brought to light by further search. In the meantime I present the following summary of these species, as representing the present state of our knowledge. I have introduced those that are doubtful as well as those fully ascertained; and have arranged them in families according to my present views of their affinities-views which may however admit of important modifications when the plants shall become better known. Summary of Fossil Plants, from beds older than the Carbonife rous system, in British America and Maine.-[Described in this paper; and in that on the Devonian plants of Gaspé, in the Journal of the Geological Society of London, Vol. 15, and Canadian Naturalist, Vol. 5.] (a).-Exogenous Gymnosperms. (1.) Prototaxites Logani, mihi,........Lower Devonian, Gaspé. (2.) Dadoxylon Ouangondianum, m.,..........St. John group. (3.) Sternbergia, (probably pith of last species), Devonian, Perry. (4.) Aporoxylon,.. Do. .....St. John. 2. Sigillaria. (5.) Sigillaria?-Cyperites?... (b.)—Doubtful if Gymnosperms or Cryptogams. (8.) Sphenophyllum antiquum, m.,.. (c.)—Acrogenous Cryptogams. (9.) Lepidodendron Gaspianum, m.,.... (12.) Lycopodites Matthewi, m., .... ..St. John. ..St. John. ..St. John. .Gaspé and Perry. .Gaspé, Perry, St. John? Gaspé. ...Gaspé. ..Perry. ....St. John. ..St. John and Gaspé. .Devonian, Kettle Point. Adding to the above the species from the Devonian of New York and Pennsylvania, described in the Reports of the Geology of those states, and in the Memoir of Goeppert above referred to, we may estimate the known land flora older than the carboniferous period in Eastern America, at about thirty species, belonging to at least fifteen genera, all cryptogamous or gymnospermous. ARTICLE XI-On the origin of some Magnesian and Aluminous Rocks. By T. STERRY HUNT, F.R.S., of the Geological Survey of Canada. (Presented to the Natural History Society.) In common with other observers, I have long since called attention to the fact that silicates of lime, magnesia and oxyd of iron are deposited during the evaporation of many natural waters, such as the mineral springs of Varennes and Fitzroy, and the waters of the Ottawa river. I have also suggested that the silicates thus produced may have contributed in a considerable degree to the formation of rocks. (Amer. Jour. Science, March, 1860, p. 284). A hydrous silicate of magnesia which approaches in composition to MgO. SiO3, combined with from ten to twenty per cent of water, and mechanically mixed with small portions of oxyd of iron, alumina, and carbonates of lime and magnesia, forms extensive beds with limestones and clays in tertiary strata, in France, Spain, Morocco, Greece and Turkey. It is the sepiolite of Glocker, the meerschaum of some authors, the magnesite of others. The quincite of Berthier, which occurs in red particles disseminated in limestone, is a similar compound, containing some oxyd of iron. The sepiolite from the basin of Paris occurs beneath the gypsiferous group, and in the lacustrine series known as the St. Ouen limestone, where it forms very fissile shaly layers, enclosing nodules of opal (menilite). The structure of this sepiolite, which I have examined and described as above, and that from Morocco, which is used by the Moors in their baths as a substitute for soap, and has been described by Damour, is peculiar. The mineral is made up of thin soft scales, and when moistened with water, swells up into a pasty mass resembling a finely divided talc. Although agreeing closely with this mineral in the proportions of silica and magnesia, sepiolite contains more water, and both before and after ignition is soluble in acids, which talc is not. We cannot however doubt that talc and steatite have been formed from sepiolite, which has undergone a chemical change and become insoluble. It is possible that serpentine may be derived from another silicate richer in magnesia than sepiolite. The frequent association of carbonates of lime and magnesia with talc, and of carbonate of magnesia, talc and serpentine, as in the ophiolite of Roxbury, would seem opposed to the notion that serpentine may have been formed from the alteration of a mixture of sepiolite and carbonate of magnesia. In chlorite, which often forms rock masses almost without admixture, we have an alumino-magnesian silicate which cannot have been derived from sepiolite, inasmuch as this contains for the amount of magnesia present, twice as much silica as chlorite. The oxygen ratios of the silica and magnesia in sepiolite are as 3: 1, and those of silica, alumina and magnesia (including the variable amount of ferrous oxyd which in part replaces the latter) in chlorite are as 6: 3: 5, while in the purest clays the ratio of silica and alumina equals 1 : 1, and in most argillaceous sediments the proportion of silica is still greater. It is evident, therefore, that chlorite could not be formed from a mixture of sepiolite with clay, or even with pure alumina, without the elimination of a large amount of silica, and we are led to regard it as having been generated by the reaction of a silicate of alumina or clay with magnesia, which was probably present in the unaltered sediment in the form of carbonate. Unless indeed the process, which according to Scheerer, has in recent times caused the deposition from waters, of neolite, a hydrous alumino-magnesian silicate approaching to chlorite in composition, be the type of a reaction which formerly generated beds of chlorite, in the same way as those of sepiolite or talc. A silicate of lime allied to sepiolite, has not so far as I am aware, yet been noticed among unaltered sediments, and among crystalline strata calcareous are more rare than magnesian silicates, although double silicates of lime and magnesia (pyroxene and hornblende,) often form beds, and wollastonite, either alone or mingled with carbonate of lime, sometimes constitute rock masses. The double silicates of alumina and lime are however abundant; the lime-feldspars, scapolite, epidote (saussurite), and white garnet, all form beds in crystalline rocks. Reactions in water at the earth's surface, and at no very elevated temperature, may have given rise to double silicates of lime and alumina corresponding to neolite, and allied in composition to the zeolites, and these by subsequent metamorphism have been changed into anhydrous silicates. The production of harmotome, chabazite, and apophyllite by the waters of a spring at Plombières, at temperatures not above 160° F. as observed by Daubrée, lends probability to such a view. But while we admit the possible direct formation of double silicates in water at ordinary temperatures, there is not wanting evidence that the reaction which we long since pointed out, (Proo Royal Society of London, May 7, 1857) between silicious and argillaceous matters and earthy carbonates, in presence of alkaline solutions intervenes in the metamorphism of sedimentary rocks and in the production of many silicious minerals. The blue Silurian limestones of the island of Montreal, when treated by acids leave an insoluble residue, which contains about ten per cent. of soluble silica, mixed with an argillaceous matter whose analysis gave silica 73·0, alumina 18.3, potash 5-5, and only traces of lime and magnesia. In the vicinity of an intrusive dolerite, however, the limestone is changed in colour, and leaves by the action of acids a greenish matter which consists of silica 40.2, alumina 9.3, peroxyd of iron 5.2, lime 36.6, magnesia 3.7. The free silica and that of the intermingled aluminous silicate, has thus been saturated with protoxyd bases, still however, retaining the alumina in combination. A similar reaction with more aluminous matters, would give rise to epidote, garnet, magnesian mica, scapolite or feldspars like labradorite and anorthite, and it is not impossible that in such reactions a portion of alumina may sometimes be set free, and give rise to corundum, spinel, diaspore or völknerite, In the ordinary modes of decomposition of minerals containing alumina, this base separates in the form of silicate, and the conditions required for its elimination in a free state are but imperfectly understood. We have elsewhere pointed out the decomposition by alkaline and earthy carbonates, of solutions of sulphate of alumina or native alum, as one source of free alumina, and insisted upon the existence of pigotite, a native compound of alumina with an organic acid, as an evidence that this base is sometimes like oxyd of iron, (and oxyd of manganese,) taken into solution by water aided by organic matters. A hydrate of alumina gibbsite, is found associated with limonite, and the aluminous minerals from the south of France described by Ber thier and Deville, show that free alumina is much more common |