On Irrigation in Tasmania. 85 
sufficient for 30,000 acres. The gates in the dam have 
been made so low (for what reason does not appear) that 
the water of the lake flows freely over them, so that, in 
fact, the dam is now of little or no use ; but this is merely 
from want of a foot or two more of planking to each 
gate. The Derwent, the Ouse, the Clyde, the Lake, the 
Macquarie, and indeed, as I believe, every other river, is 
provided with these most invaluable natural basins; 
even those alone which are marked in the maps pro¬ 
bably contain more than 200 square miles of surface, 
which, carried to the depth of one yard only, would 
supply water throughout the summer for 300,000 acres, or 
up to the time of harvest for about 1,000,000 acres. 
It must be observed, too, that these lakes and lagoons 
are generally situated very high up in the hills, where the 
land is of very little value. In this respect, therefore, 
probably Tasmania stands unrivalled in its natural 
advantages for storing up water during the rains. 
Besides the water that may be thus stored up by em¬ 
banking the lakes and lagoons, many of the rivers have 
a considerable body of water flowing down them 
throughout the summer, which may be diverted merely 
by dams and channels, and spread over the lands : this is 
the case with the Derwent and those of its feeders which 
come from the southward, with the North and South 
Esk, and the rivers to the west of Launceston. No 
portion of this water ought to be allowed to reach the 
sea in the summer, excepting, indeed, land could not be 
found within reach of a river sufficient to absorb the 
whole of its stream : but this could not be the case with 
any of the rivers except the Derwent, and perhaps not 
with that. 
As an instance of the facility of storing up water, the 
case of the Macquarie may be quoted. The lagoon at 
the head of the southern branch of that river was shut 
