RICH IN PHOSPHATE OF LIME.

281

Near the point where it crosses the Ottowa, a branch of this formation forks off towards the south, spreads over a considerable extent of country between the Ottowa and the head of the St Lawrence, crosses this river at the Thousand Isles, among which the syenitic rocks prevail, with intermixed crystalline limestones, and passes into the northern counties of New York, where it is extensively developed. It is there coloured among the primary rocks of the State, in the published geological maps of Mr Hall and Professor Emmons.

This rock, like the altered limestones in most other localities, contains imbedded in it various simple minerals in greater or less quantity; and among these apatite, or phosphate of lime in grains and green crystals, is sometimes very abundant. Mr Logan, Provincial Geologist for the Canadas, in his Report for 1845-46, p. 94, has mentioned several localities where the mineral phosphate of lime is especially plentiful; and Mr Hunt, chemist to the survey, with whom I had the pleasure of conversing upon the subject, assured me that in many places this mineral formed a tenth part of the whole rock.

One economical fact is certain-that the existence of such a limestone is of undoubted value to the neighbourhood in which it exists, where it can be readily quarried and burned for lime, to be used in agricultural operations; and that it is of equal value as an article of export for agricultural purposes, where facilities for shipment or other cheap means of transport exist. Such a limestone rock, in most easily accessible parts of Great Britain, would be as sure a source of permanent wealth as a mine of Californian gold.

Another economical point is worthy of inquiry. Does this mineral phosphate, in any of these localities, occur

* At Blasdells Mills, on the Gateneau, at the Calumet Slide, and above the head of Moor's Slide, near the line between Ross and Westmeath. Probably many other localities are now known.

282

PHOSPHATE OF LIME ABUNDANT.

in masses so large, or so readily separable from the common limestone, that it could be economically extracted, and brought in a pure state into the market? If so, it would prove valuable as an article of shipment to Europe, and would provide another available resource to the high-farmed lands of Great Britain. Upon the exhausted wheat-soils of Canada, properly prepared and applied, its use would be invaluable. An inquiry into this point is deserving of the attention of the Canadian Legislature, with a view to the good of the province; and of individual landowners along the outcrop of this rock, with a view to their own individual profit.

I think it the more likely that some localities may be found in Canada where this mineral phosphate will present itself in sufficient quantity to admit of being profitably extracted, because, during my subsequent residence in the State of New York, I was assured by Professor Emmons of Albany, one of the State geologists, that he had met with it in several places in that State where he thought it might be so extracted. In the white metamorphic limestones of Essex, Jefferson, and St Lawrence Counties, into which, as I have already said, the Canadian limestone extends, he had so observed it; and at Rossie, in the last of these counties, he thought a man might in some places pick out a hundredweight a-day. Among the magnetic iron ores also, in the township of Peru, near Lake Champlain, he informed me that it sometimes occurs in equal bulk with the ore itself, and that, by washing or other mechanical means, a ton a-day might be collected in some localities.

In the interest of general scientific agriculture, independent of individual or local profit, it is desirable that the accuracy of such statements, and the possible availability of these and similar deposits, should be speedily investigated.

MINERALS IN METAMORPHIC ROCKS.

283

Speculations have been hazarded at various times in regard to the origin or source of the crystals of apatite (phosphate of lime,) of graphite (plumbago,) garnets, and various other minerals, which are met with in so many countries intermingled with the metamorphic or crystalline limestones. But the origin of all these is now easily intelligible. It is certain that this crystalline character is the result of the action of heat long continued. But the assumption of this crystalline character implies a power of movement of the particles among each other, which, in fact, is seen in many cases in unmelted bodies-as in the annealing of glass and metals, and in the tempering and converting of iron or bronze-to take place where they are kept for a prolonged period at an elevated temperature. It is certain, also, that particles of a like kind have a special attraction for each other—a tendency to draw towards one another and cohere, when circumstances are such as to admit of their moving among themselves, or among the particles of other matter with which they may be mixed. And, thirdly, it is certain that, when several substances which incline to unite with each other are present in a mixture in which circumstances admit of a movement among the particles, they often unite to form definite chemical compounds, exhibiting, more or less, well-defined crystalline forms.

Now it is known that stratified limestones, when deposited, are rarely free from admixtures of earthy matter, which contain the constituents of garnet, chondrodite, hornblende, &c. When these limestones are subsequently exposed to the long-continued action of heat, the particles of the rocky mass arrange themselves in crystalline forms, while the earthy matters unite to form the simple minerals (garnet, &c.,) which can be most readily produced out of the substances of which they consist, in the proportions in which they are actually

284 PRODUCTION OF CRYSTALS, OF PHOSPHATE

present. Hence the minerals produced differ in quantity, in kind, and in relative proportions, according to the quantity and nature of the impurities which the limestone contains.

Again, all limestones, almost without exception, contain the remains of animals or vegetables, or both. In the former they are often very rich, and in these phosphate of lime always exists in sensible quantity. When the limestone is changed by heat, the animal and vegetable substances are at the same time entirely decomposed. All that is volatile escapes; while the earthy phosphate, being fixed, remains intermixed with the limestone. But while the particles of carbonate of lime attract each other, and form crystalline marble, those of phosphate of lime also attract each other, and, although sparingly mixed up with the limestone, gradually approach each other, and finally cohere into crystalline grains, and regularly crystallised forms. In this way the phosphate, which was intermixed with the rocky mass, perhaps in almost inappreciable proportion, becomes collected together into sensible masses in particular places. And if the rock be one which, like some of our still unchanged limestones, is unusually rich in animal remains, or in mineral phosphates as a mass, the quantity of the separated crystals will be great in proportion. Hence their comparative abundance in some of these white limestones, and hence also the reason why the occurrence of them may be looked for, in some localities, in sufficient quantity to admit of their being economically extracted for use in agriculture or the arts.

Lastly, while the volatile parts of the animal and vegetable matters contained in the limestone-those which often give to limestones a bituminous character— escape under the influence of heat, a portion of the more fixed charcoal (carbon) remains, in the crystallised form of graphite or plumbago. Hence, the deposits of this

OF LIME, AND OF GRAPHITE.

285

substance, more or less extensive, which are frequently met with in metamorphic limestones-varying in amount with the quantity and kind of organic matter which the rock originally contained, and with the intensity and continuance of the heat to which it has been exposed. In some places in Canada, and in the State of New York, therefore, it may still be found in sufficient quantity to prove an invaluable source of mineral wealth.

If what is above said, in regard to the phosphate of lime, be received as a satisfactory explanation of its origin, it will follow that crystalline limestones in which this mineral is found must not only be metamorphic, but must have been deposited in the stratified form, and have once contained the remains of fossil animals in very considerable quantity.

I may here, in connection with this metamorphic limestone of Canada, mention three facts observed by Mr Logan,* which are not only interesting in themselves, but which bear upon the important point in chemicogeological theory-the supposed origin of such limestones, to which I have just alluded. These facts are-First, That while the gneiss above or below the limestone exhibits regular stratification and even lamination, the limestone itself will at times display contortions of the most complicated character, and which increase in importance with the thickness of the bed of limestone. Second, That when this thickness is great, beds of gneiss, of even a foot in thickness, will be bent, folded, and broken, and fragments--sometimes very large--of the gneiss will be surrounded by the white limestone. Third, That, in one instance, the bed of limestone had an uninterrupted connection with a mass of the same, which filled up a crack or fault in the gneiss, at right angles to the general direction of the strata. In the large, the limestone and

Survey of Canada Report for 1845 and 1846, p. 43.