By examination of Table III. we perceive that the summer temperature of Fort Enterprise is found at Churchill, in latitude 59°; the neighbourhood of the ice which floats in Hudson's Bay until August, compensating, in this case, for a difference of 64 degrees of latitude. The isotheral line, carried across to the Old Continent, passes near to Enontekies.

In no part of the barren grounds did we discover the ground to be perpetually frozen. The subsoil, however, at York-Factory is always frozen, a circumstance which is also to be attributed to the constant presence of ice in the Bay during the summer. The thaw at York, (latitude 57°) in September, was observed to penetrate three feet.

In latitude 65° the sap of the spruce-tree freezes early in October, and in a short time the wood becomes as hard as a stone, the chips produced by a highly tempered hatchet being similar to saw-dust. The hatchets are speedily broken in this employment, which renders the Indians anxious to find dead and dry trees for winter use; and to procure a constant supply of this kind of fuel, they occasionally set fire to a clump of trees, expecting to find their trunks fit for use in two or three years.

At Slave Lake, where our attention was directed to this subject, the sap of all the other trees, and of the juniper-bush and other shrubs, was observed to freeze equally with that of the white spruce. The power of the direct rays of the sun upon the trees, causes them to show signs of returning life before the earth acquires any warmth, and the ground about the roots of the larger trees is first cleared of snow,

and thawed.

Having, in the preceding details of climate, mentioned the circumstances most likely to influence the distribution and growth of vegetables in the

districts travelled through, I may remark, that the agency of man, so powerful in modifying the appearance of the vegetable kingdom in other quarters of the globe, is scarcely to be detected in these remote lands. Cultivation of the ground is entirely confined to a few small gardens at the furposts, and the utmost effect that can be ascribed to it, is the introduction of a few herbs from Canada and Europe, along with the Cereala and culinary vegetables. The majority of the introduced plants is perhaps comprised in the following brief list of the species, which were found only in the direct trading route; but several, even of these, may nevertheless be indigenous:-Blitum capitatum, Veronica peregrina, Lycopus Virginicus, Hordeum jubatum, Myosotis lappula, Rumex acutus, Cerastium viscosum, Spergula nodosa, Euphrasia officinalis, Lepidium ruderale, Atriplex Urtica gracilis.

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The only mode in which the arts and customs of the natives affect the vegetable kingdom, is by their setting fire, either accidentally or intentionally, to the forests. These fires, when they occur during summer in the woody district, spread rapidly through the dry moss, consuming the soil down to the rocks, and are only extinguished by heavy showers of rain. Several years elapse before anything grows in the district thus laid waste. The blackened and branchless trunks of the trees are in a season or two stripped of their bark, and bleached, if not sooner thrown down by the wind. The surface of the ground next acquires a little verdure from the Funaria hygrometrica, Bryum pyriforme, Didymodon purpureum, Marchantia polymorpha and conica, and some other Musci and Hepatica. By and by other vegetables take root, and in process of time the site of a pine-forest is occupied by dense thickets of slender as

pens (Populus trepida). The growth of this tree, instead of a renewal of the pine-forest, may be attributed either to a change in the nature of the soil, perhaps by the introduction of a great er quantity of alkaline matter,-to its winged seeds favouring its dispersion, or to both causes conjoined. The ashes of the poplar yield much more alkali than those of any of the pines do.

Fires frequently spread amongst the

dry grass in the plains of Carlton House; but their principal effect there seems to be the production of finer pasture in the following season. They do not seem in general severe enough to destroy the roots of the grass, or to burn the soil. The migrations of the herds of the bison or buffalo, are much influenced by the extent and direction' of these fires.