One great source of true graphite for many years was the famous mine at Borrowdale, in Cumberland, but this is now almost exhausted.  The vein lay between strata of slate, and was from eight to nine feet thick.  As much as L100,000 is said to have been realised from it in one year.  Extensive supplies of graphite are found in rocks of the Laurentian age in Canada.  In this formation nothing which can undoubtedly be classed as organic has yet been discovered.  Life at this early period must have found its home in low and humble forms, and if the eozooen of Dawson, which has been thought to represent the earliest type of life, turns out after all not to be organic, but only a deceptive appearance assumed by certain of the strata, we at least know that it must have been in similarly humble forms that life, if it existed at all, did then exist.  We can scarcely, therefore, expect that the vegetable world had made any great advance in complexity of organism at this time, otherwise the supplies of graphite or plumbago which are found in the formation, would be attributed to dense forest growths, acted upon, after death, in a similar manner to that which awaited the vegetation which, ages after, went to form beds of coal.  At present we know of no source of carbon except through the intervention and the chemical action of plants.  Like iron, carbon is seldom found on the earth except in combination.  If there were no growth of vegetation at this far-away period to give rise to these deposits of graphite, we are compelled to ask ourselves whether, perchance, there did not then exist conditions of which we are not now cognisant on the earth, and which allowed graphite to be formed without assistance from the vegetable kingdom.  At present, however, science is in the dark as to any other process of its formation, and we are left to assume that the vegetable growth of the time was enormous in quantity, although there is nothing to show the kind of vegetation, whether humble mosses or tall forest trees, which went to constitute the masses of graphite.  Geologists will agree that this is no small assumption to make, since, if true, it may show that there was an abundance of vegetation at a time when animal life was hidden in one or more very obscure forms, one only of which has so far been detected, and whose very identity is strongly doubted by nearly all competent judges.  At the same time there may have been an abundance of both animal and vegetable life at the time.  We must not forget that it is a well-ascertained fact that in later ages, the minute seed-spores of forest trees were in such abundance as to form important seams of coal in the true carboniferous era, the trees which gave birth to them being now classed amongst the humble cryptogams, the ferns, and club-mosses, &c.  The graphite of Laurentian age may not improbably have been caused by deposits of minute portions of similar lowly specimens of vegetable life, and if the eozooen the “dawn-animalcule,” does represent the animal life of the time, life whose types were too minute to leave undoubted traces of their existence, both animal life and vegetable life may be looked upon as existing side by side in extremely humble forms, neither as yet having taken an undoubted step forward in advance of the other in respect to complexity of organism.