168 
On Irrigation in Tasmania . 
The best mode of construction in Tasmania would 
probably be by means of large timbers laid flat and 
trenailed together into a frame-work, which is to be 
filled up with large stones : such a work has been con¬ 
structed by Captain Fenton at Fenton Forest, in the 
torrent called Russell’s Falls, and appears to be admi¬ 
rably suited to the circumstances of the colony. The 
material point to be attended to in such a dam, is to 
prevent its being undermined on the lower side by the 
fall of the water. If the bed be rocky, it is of course 
secure by nature; but if the bottom be clay or gravel, the 
bed must be covered witli large stones of from £ to 1 ton 
weight for some yards below the dam : the ends must 
also be protected by rough stonework, to prevent the 
water cutting through the natural ground, and forming 
channels round the work. 
But, besides what may be done by means of the rivers 
and larger reservoirs, a great number of estates may be 
watered to a considerable extent by means of small basins 
or marshes, which, as has been stated, are so generally to 
be found high up the courses of the smaller creeks. A 
very great number of estates have such natural advan¬ 
tages ; by following up the creeks to their sources, it will 
be discovered whether any basins do exist: it should be 
observed that they will generally be found high up in the 
hills, and not near the points where they enter the plains. 
A marsh of 30 acres in extent, closed at its outlet so as to 
contain a depth of water of 3 yards, would supply suffi¬ 
cient to irrigate about 180 acres through the whole 
summer, or 540 acres of grain land. 
Lastly, in many situations water may be raised for 
irrigation by machinery: the situations suitable for this 
are the shores of the lakes, and the banks of those rivers 
which have deep channels. The peculiar advantage of 
this method is, that in many parts any individual propri- 
