THE SAULT ST LOUIS. 279 same tact appeared, but with a greatly superior intellectual skill, in handling and guiding a large boat with a heavy cargo through a crooked channel, where the slightest oversight, for a single moment, would cast all upon the rocky shallows. Let the reader fancy to himself a ledge of rocks running across the river, over which the water has a distinct fall to the eye appearing to be somewhere between six and ten feet-into deep water below. Through this ledge is a narrow channel of deep water, where the rock has been torn away, and through which the river rushes with great velocity. Below this ledge, at a short distance, is a second ledge of rock, over which the water falls, and through which, as in the case of the first, a natural gap or sluice-way exists. Between these two ledges deep water exists, but the openings of the two are not opposite to each other, or in the same line. You must descend the one, then turn sharp in the deep water along the foot of the first ledge, and at the proper time turn sharp again to go through the other. The channel is a true zigzag, and to sail along this letter Z in the face of a strong current, and a heavy pressure of water, requires a degree of skill and coolness in the captain, and of mobility in the ship, which it requires a little consideration fully to realise. Four men at the wheel, and six at the tiller, to guard against accidents, steered us safely down; and it was beautiful to see with what graceful ease and exactness the prow of the long vessel turned itself to suit the sudden turns of the rocky channel. We reached Montreal about nine o'clock, soon after which, a pelting rain came on the first serious fall of rain I had yet encountered on the American continent. The approach to Montreal from the river reminded me of the approach to Leith from the river Forth. The town of Montreal on the river bank, and the hill of 280 METAMORPHIC LIMESTONE Mont Royal rising behind with a faint resemblance to Arthur's Seat, sent the heart home to more familiar scenes, and almost secured beforehand for the strangercity an interest in its affections. In descending the St Lawrence from Kingston, the somewhat naked and rocky limestone country of that part of Upper Canada continues, till we have passed the Thousand Isles. Below this the banks are less rocky, and most of the way down to Montreal consist of a light-coloured drift, which yields in general, I should think, only an indifferent soil. This drift rests upon, and is probably in great part formed from, the Potsdam sandstone and calciferous sand-rock of the New York geologists-being the lowest portions of the Lower Silurian rocks. These rocks, where they occur in other parts of North America, produce in general inferior soils. The most interesting geological fact, bearing upon the practice of agriculture, which fell under my observation in this part of my tour, is the occurrence over a large part of Canada of a deposit of metamorphic limestone, which is unusually rich in phosphate of lime. This limestone is subordinate to, and interstratified with, beds of porphyritic and syenitic gneiss, which form a long ridge of high-land, dipping beneath not only all the Silurian strata, but also under the copper-bearing beds of Lake Superior, which are beneath the Silurian. Both the limestone and the gneiss are probably highly altered members of the older Cambrian series. This ridge of altered rocks extends, as a prolonged high-land, in a north-east and south-west direction, from the west of Labrador to the Ottowa, running nearly parallel to the St Lawrence, and at a distance north of that river of from twelve to twenty miles. Near Bytown on the Ottowa the limestone appears in great force, and from that point the ridge of mixed rocks ranges nearly due west to the shores of Lake Huron. 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 |