On Irrigation in Tasmania . 
171 
EXPENSE OF IRRIGATION. 
This will, of course, vary greatly according to situation; 
but an example of the probable cost of effecting it in 
each of the ways mentioned, taken from observation of 
particular localities in the colony, may be useful. 
Cost of Tanks. —This, in the case of using the large 
lakes and lagoons for this purpose, will be comparatively 
insignificant. To raise the water in one of the lakes one 
yard by means of a timber or stone work at the outlet, 
would not, as in the case of the lakes at the head of the 
Clyde, cost more than from £20 to £50; and as this 
might retain water enough for from 10,000 to 30,000 
acres, it is evident that it would scarcely be felt at all. In 
smaller lagoons or marshes—for instance, in an area con¬ 
taining 1000 acres—an embankment of sufficient height 
to retain four yards of water might be constructed for 
£300, where the outlet is (as it usually is) narrow; and 
as such a reservoir would irrigate 10,000 acres, the cost 
per acre would still be imperceptible. In a small marsh 
containing 30 acres, with a less favourable outlet, it 
would cost perhaps £200 to retain three yards of water; 
and as this would supply about 540 acres of grain land, 
it would amount to less than 8s. per acre of such land, 
and to three times that amount, or 24s. per acre, of grass 
to be watered throughout the summer : this is the prin¬ 
cipal ; the annual interest at 10 per cent, would be about 
10 d. and 30 d. per acre respectively, and still therefore of 
little consequence further than as requiring so much 
capital. 
Channels .—In a tolerably favourable situation, a 
channel from one of the large rivers of two miles in 
length might water 200 acres, and cost £400, including 
a considerable quantity of blasting or troughing at the 
commencement; being £2 per acre in the first outlay, or 
