Page:The journal of the Royal Geographic Society of London. Volume 34, 1864. (IA s572id13663720).pdf/265

Rh tentlon to the fickle and uncertain winds that prevail on the lakes. This phenomenon is accounted for on the principle in pneumatics that underlies the explanation of all motions in the atmosphere, viz., the tendency of cold air to supply the place of the warmer and more rarefied. The secondary causes are the unequal radiating powers of land and water, and more especially, in this case, in the very unequal and mountainous surface of the country surrounding the lakes; the cold mountain air descends into the gullies, and they all open into the lakes. Then, again, they lie in different directions, and so receive the heat of the sun at different times of the day. The consequence of these varied influences at work is a condition of unstable equilibrium in the atmosphere, which, when intensified by a strong north-west wind (the prevailing wind) raises a sea on the lakes that—confined within their narrow limits and broken on many headlands and islands—becomes for the time a tumultuous assemblage of waters, against which it is in vain for human effort to contend. The action of the winds on the Te Anau Lake, from its greater size and diversity of shape, is more interesting than on any of the other lakes. On it there is sometimes both a storm and a calm at the same time. Sometimes it will blow down the lake, and at the same time be calm up the fiords, or vice versâ. When such is the case, there is a sort of heaving motion over the calm part. During warm settled weather the phenomenon of “land and sea-breeze,” so grateful in warm countries, prevails on the lakes. On the Te Anau Lake, where, on account of the large extent of downs on its east side, the radiation is more regular than that which arises from the surroundings of some of the other lakes, this alternating breeze during the intervals it operated was seen to be so regular, morning and evening, that it became almost a measure of time; and from the tidal effects that the breeze had on the Te Anau, it seemed to confer on it the attributes of a sea.

Rivers.—The two principal rivers of the country surveyed are the Waiau and Kawarau; these, together with the Upper Oreti and Wakaia; represent the drainage of the country. The Waiau issues from the Te Anau Lake, and after a very rapid sinuous course of 10 miles, it enters the Manipori Lake at a distance of 5 miles in a direct line from its exit from the Te Anau; after mingling its waters with those of the Manipori Lake, the Waiau leaves it at a distance of 6 miles south from where it entered it. For the first 5 miles of its course, after leaving the Manipori Lake, the Waiau flows east by south in a slow sluggish manner; at that distance it receives the Mararoa, a very considerable tributary; it then suddenly bends to the south, and at the same time quickens its current; it then pursues a rapid course of upwards of 40 miles, in a general direction very nearly due south, when it falls into the