a—3.

interesting to give a comparison of the length and drainage areas of the principal rivers in the world, with their approximate mean discharge.

It will be seen from the above table that the Clutha may only be rated amongst the lesser rivers; still, for the area of its drainage-basin, it discharges as much, if not more, than any river in the world. It discharges over 3 cubic feet per second for every square mile of its drainagebasin. In reference to the benefits to be derived by the construction of the locks, they no doubt would enable a large number of miners to get a little gold during the time the locks were shut down, and possibly in a very dry winter these locks might be closed for twenty-four days ; but then it would take a considerable time to draw off the water to its original level before the gates could be again closed. The quantity of tailings and gravel now in the bed of the river would prevent much gold being obtained by manual labour, as every time the gates were opened the bed of the river would be all levelled, so that no trace of a paddock formerly taken out would be left. The only portion of the river that could be worked to advantage would be on the sides and in the crevices of the rock. The scheme is purely one of policy, and becomes a question of pounds, shillings, and pence, as to whether the benefits to be derived would justify the expenditure. If the Government undertook works of this character the only direct benefit would go to the counties for additional goldfields revenue, and whatever collateral advantages might be derived would be in the shape of indirect revenue through the Customs. Before an estimate could be given of the cost of constructing locks, surveys would have to be made, and plans prepared ; but one thing is certain—that no works of a temporary character could possibly be constructed at either of the outlets from these lakes. The difficulty in getting down proper foundations, so as to insure the stability of the works, would in itself be a great item in the cost of construction, especially in the Clutha and Kawarau Bivers, where a very large allowance would have to be made for unforeseen contingencies. The volume of water is large ; but the greatest trouble to contend with is the very high velocity of the current, with the possibility of floods during the time the works were in construction. Any estimate now given has to be taken as purely an approximate one, which may be set down as follows : — Lock at Hawea Lake ... ... ... ... ... ... £12,000 Lock at Wanaka Lake ... ... ... ... ... ... 70,000 Lock at Wakatipu Lake ... ... ... ... ••■ 45,000 Total £127,000 The construction of these locks would also necessitate men being steadily employed at each, so as to lift and regulate the gates, and to attend to everything connected with them ; and this expense

104

Kiver. i Drainage- j g basin g in Square '£, Miles. tb B 8.2 g H 3 0) is S ■ j.a p, I River. Drainagebasin in Square Miles. o I ttO CI o> © -+3 s 2 g iz'i Europe — • Volga Danube Don ... Petchora Dneiper Rhone Rhine Elbe... Tagus Loire... Dneister Po ... Oder... Guadiana Asia — Yenisei Obi-Irtish Lena... Amur Yang-tze-Kiang Hoang-Ho Brahmaputra ... Indus Ganges Tigris-Euphrates Mehong Sir-Daria 527,000 306,000 176,000 114,400 195,000 37,000 75,000 55,000 33,000 44,500 27,300 34,600 45,200 25,000 2,400 1,795 995 900 750 645 600 550 540 530 500 450 445 400 384,000 207,000 125,000 72,000 136,000 25,000 51,750 37,000 20,000 25,000 19,500 20,000 26,000 17,500 Asia (continued) — Amu-D aria Irawady ... Africa — Congo Nile Niger Zambezi ... Orange Limpopi ... Cubango ... Senegal Shari Gambia ... America — Mississippi-Missouri Amazon La Plata ... Mackenzie Tocantus ... Eio Grande del Norte San Francisco St. Lawrence Orinoco Columbia ... Colorado ... New Zealand — Clutha-Kawarau 193,000 220,000 1,300,000 1,085,000 900,000 500,000 418,000 216,000 300,000 170,000 300,000 30,000 900 1,800 2,883 4,020' 2,300: l,400 : 1,0001 990| 950| 900! 810; 650 423,000 350,000 432,700 118,900 107,010 59,450 57,000 34,500 35,670 26,000 35,000 3,750 1,180,000 1,400,000 1,000,000 807,000 722,000 387,000 370,000 370,000 432,500 259,000 216,000 237,920 2,950 2,800 2,600 2,920 3,158 2,600 2,000 1,980 1,600 1,496 1,250 1,000 416,000 590,000 379,000 372,000 349,600 242,300 350,000 312,000 203,485 76,000 138,000 151,000 1,250,000 2,275,000 1,242,000 590,000 285,000 245,000 187,000 410,000 400,000 298,000 257,000 4,194 3,545 3,063 2,868 1,500 1,400 1,300 2,000 1,200 1,020 1,000 675,000 1,300,000 830,000 195,000 203,000 172,000 8,406 210 27,866