It is evident to observers who have recorded facts respecting the lakes, that but a small amount of vapour water is deposited by northeasterly winds from the Gulf of St. Lawrence, the great estuary of that river, of which the lakes are only enlargements, as the wind from that region carries the cloud-masses from the lakes themselves direct to the valley of the Mississippi. For it meets with no obstacle from high lands on the western littorale, which is low. A north-east gale continues usually from three to six days, and generally without much rain; but all the other winds from south to westerly afford a plentiful supply of moisture. Thus a shift of wind from north-east to north and to north-west perhaps brings back the vapour of the great valley of the gulf, reduced in temperature by the chilly air of the north and west. If then an easterly gale continues for an unusual time, the basin of the Canadian lakes is robbed of much of its water, which passes to the rivers of the west, and is lost in the gulf of Mexico, or in the forest lakes of the wild West. Perhaps, therefore, whenever a cycle occurs in which north-east winds prevail during a year or a series of years, the lakes lose their level, for, their direction being north-east and south-west, such is the usual current of the air; and therefore either north-east or south-westerly winds are the usual ones which pass over their surface. The parts of the great inland navigation which suffer most in these periodical depressions are the St. Clair River and the shallow parts of those extensions of the St. Lawrence called Lakes St. Francis and St. Peter, which in the course of time will cause, and indeed in the latter already do cause, some trouble and some anxiety. The north winds, keen and cold, do not deposit much in the valley of the lakes, whose southern borders are usually too low also to prevent the passage of rain-bearing clouds. From that portion of the dividing ridge between the valleys of the St. Lawrence and Mississippi, only seven miles from Lake Erie, says an American writer, there is to Fort Wayne, at the head of the Maumee river, one hundred miles from the same lake, a gradual subsidence of the land from 700 to less than 200 feet. From Fort Wayne westward this dividing ridge rises only one hundred and fifty feet, and then gradually subsides to the neighbourhood of the south-west of Lake Michigan, where it is but some twenty feet above the level of that water. The basin of the Mississippi, including its great tributary streams, receives therefore a very great portion of the falling vapour, from all the winds blowing from north to north-east.