F PLANTS. hat the quantity of hat in similar areas Iso to be observed ars to be occupied es, and that rich ation of this sysrocks believed to swick, there is a d associated with ng an aggregate e present world, cose organic reose of the Laulized carbon in atter, and that in the first inacid by living I believe, be may, however, e Laurentian coal, or that er similar to bituminous aphite near nderoga in , and elseone might of Rhode ional, and n graphite nce to the mestones. Society," vol. We may compare the disseminated graphite to th which we find in those districts of Canada in which Sil rian and Devonian bituminous shales and limestones ha been metamorphosed and converted into graphitic roc not very dissimilar to those in the less altered portions the Laurentian.* In like manner it seems probable th the numerous reticulating veins of graphite may ha been formed by the segregation of bituminous matter in fissures and planes of least resistance, in the manner which such veins occur in modern bituminous limeston and shales. Such bituminous veins occur in the Low Carboniferous limestone and shale of Dorchester a Hillsborough, New Brunswick, with an arrangement ve similar to that of the veins of graphite; and in the Qu bec rocks of Point Levi, veins attaining to a thickness more than a foot, are filled with a coaly matter having transverse columnar structure, and regarded by Loga and Hunt as an altered bitumen. These paleozoic anal gies would lead us to infer that the larger part of t Laurentian graphite falls under the second class of d posits above mentioned, and that, if of vegetable origi the organic matter must have been thoroughly disi tegrated and bituminised before it was changed in graphite. This would also give a probability that t vegetation implied was aquatic, or at least that it w accumulated under water. Dr. Hunt has, however, observed an indication of to restrial vegetation, or at least of subaerial decay, in t great beds of Laurentian iron-ore. These, if formed the same manner as more modern deposits of this kin would imply the reducing and solvent action of su stances produced in the decay of plants. In this ca such great ore-beds as that of Hull, on the Ottawa, seven * p. 599. Granby, Melbourne, Owl's Head, &c., "Geology of Canada," 18 feet thick, or that near Newborough, two thick,* must represent a corresponding qua table matter which has totally disappeared added that similar demands on vegetable deoxidising agent are made by the beds metallic sulphides of the Laurentian, tho the latter are no doubt of later date than th rocks themselves. It would be very desirable to confirm such as those above deduced by the evidence of a scopic structure. It is to be observed, h when, in more modern sediments, Algæ ha verted into bituminous matter, we cannot o tain any structural evidence of the origin of su and in the graphitic slates and limestones the metamorphosis of such rocks no organ remains. It is true that, in certain bitum and limestones of the Silurian system, shred tissue can sometimes be detected, and in so in the Lower Silurian limestone of the La Clo ains in Canada, the pores of brachiopodous the cells of corals have been penetrated by minous matter, forming what may be regarded injections, sometimes of much beauty. In cor with this, while in some Laurentian graphitic for instance, in the compact graphite of Cla carbon presents a curdled appearance due to s and precisely similar to that of the bitume modern bituminous rocks, I can detect in th limestones occasional fibrous structures whic remains of plants, and in some specimens. lines, which I believe to be tubes of Eozoon by matter once bituminous, but now in th graphite. ב , two hundred feet ng quantity of vege peared. It may be etable matter as a beds and veins of , though some of an the Laurentian such conclusions e of actual microd, however, that e have been connot ordinarily obof such bitumen, nes derived from ganic structure Cuminous shales reds of organic some cases, as Cloche Mountous shells and by black bituded as natural orrespondence tic rocks, as, arendon, the segregation, en in more e graphitic ch may be vermicular penetrated e state of When paleozoic land-plants have been converted in graphite, they sometimes perfectly retain their structur Mineral charcoal, with structure, exists in the graphit coal of Rhode Island. The fronds of ferns, with the minutest veins perfect, are preserved in the Devoni shales of St. John, in the state of graphite; and in t same formation there are trunks of Conifers (Dadoxyl Quangondianum) in which the material of the cell-wa has been converted into graphite, while their caviti have been filled with calcareous spar and quartz, t finest structures being preserved quite as well as in co paratively unaltered specimens from the coal-formation No structures so perfect have as yet been detected in t Laurentian, though in the largest of the three graphi beds at St. John there appear to be fibrous structure which I believe may indicate the existence of land-plan This graphite is composed of contorted and slickensid laminæ, much like those of some bituminous shales a coarse coals; and in these are occasional small pyrito masses which show hollow carbonaceous fibres, in sor cases presenting obscure indications of lateral pores. regard these indications, however, as uncertain; and it not as yet fully ascertained that these beds at St. Jol are on the same geological horizon with the Lower La rentian of Canada, though they certainly underlie t Primordial series of the Acadian group, and are sep rated from it by beds having the character of the H ronian. There is thus no absolute impossibility that distin organic tissues may be found in the Laurentian graphi if formed from land-plants, more especially if any plan existed at that time having true woody or vascular tissue but it cannot with certainty be affirmed that such tissu * "Acadian Geology," p. 535. In calcified specimens the structu remain in the graphite after decalcification by an acid. have been found. It is possible, however, that in the Laurentian period the vegetation of the land may have consisted wholly of cellular plants, as, for example, mosses and lichens; and if so, there would be comparatively little hope of the distinct preservation of their forms or tissues, or of our being able to distinguish the remains of land-plants from those of Algæ. We may sum up these facts and considerations in the following statements: First, that somewhat obscure. traces of organic structure can be detected in the Laurentian graphite; secondly, that the general arrangement and microscopic structure of the substance corresponds with that of the carbonaceous and bituminous matters in marine formations of more modern date; thirdly, that if the Laurentian graphite has been derived from vegetable matter, it has only undergone a metamorphosis similar in kind to that which organic matter in metamorphosed sediments of later age has experienced; fourthly, that the association of the graphitic matter with organic limestone, beds of iron-ore, and metallic sulphides greatly strengthens the probability of its vegetable origin; fifthly, that when we consider the immense thickness and extent of the Eozoonal and graphitic limestones and iron-ore deposits of the Laurentian, if we admit the organic origin of the limestone and graphite, we must be prepared to believe that the life of that early period, though it may have existed under low forms, was most copiously developed, and that it equalled, perhaps surpassed, in its results, in the way of geological accumulation, that of any subsequent period. Many years ago, at the meeting of the American Association in Albany, the writer was carrying into the room of the Geological Section a mass of fossil wood from the Devonian of Gaspé, when he met the late Professor Agassiz, and remarked that the specimen was the remains of a Devonian tree contemporaneous with his fishes of that age. "How I wish I could sit under its shade!" was the smiling reply of the great zoologist; and when we think of the great accumulations of Laurentian carbon, and that we are entirely ignorant of the forms and structures of the vegetation which produced it, we can scarcely suppress a feeling of disappointment. Some things, however, we can safely infer from the facts that are known, and these it may be well to mention. The climate and atmosphere of the Laurentian may have been well adapted for the sustenance of vegetable life. We can scarcely doubt that the internal heat of the earth still warmed the waters of the sea, and these warm waters must have diffused great quantities of mists and vapours over the land, giving a moist and equable if not a very clear atmosphere. The vast quantities of carbon dioxide afterwards sealed up in limestones and carbonaceous beds must also have still floated in the atmosphere and must have supplied abundance of the carbon, which constitutes the largest ingredient in vegetable tissues. Under these circumstances the whole world must have resembled a damp, warm greenhouse, and plants loving such an atmosphere could have grown luxuriantly. In these circumstances the lower forms of aquatic vegetation and; those that love damp, warm air and wet soil would have. been at home. If we ask more particularly what kinds of plants might be expected to be introduced in such circumstances, we may obtain some information from the vegetation of the succeeding Palæozoic age, when such conditions still continued to a modified extent. In this period the clubmosses, ferns, and mare's-tails engrossed the world and grew to sizes and attained degrees of complexity of structure not known in modern times. In the previous Laurentian age something similar may have happened to Algæ, to Fungi, to Lichens, to Liverworts, and Mosses. The Algae may have attained to gigantic dimensions, and, с |