70 Bemarlcs on the Tieport of tlie Water Oommission. 



to the bant, or obliquely across it to the opposite side, until a 

 level has been reached where the lowest part of the bed of the 

 river is higher than the mouth of the channel. As, however, 

 these weirs require annual re-construction, they become in course 

 of time more expensive than the permanent construction of 

 rough stone, and are not now so generally used as they were 

 formerly." 



" The natives have, as a rule, selected rock for the foundation 

 for dams, and it is no doubt preferable to any other, both as 

 regards economy and stability. A rock foundation is not however 

 absolutely necessary, as has been fully proved under British 

 rule in India ; — many works having been constructed on rivers, 

 the beds of which consist entirely of sand. No better example 

 of such masonry work could be found than the anient across the 

 Kistnah river ; the leugth of this anient is nearly 3S00 feet, the 

 breadth 300 feet, and the height in front is 21 feet above the 

 deep bed, and 14 feet above the summer level of the water. It 

 consists of a mass of rough stones thrown into the river and 

 allowed to assume its own slope." 



These illustrations of Indian engineering are suiEcient to show 

 that rivers may be dammed by rubble breakwaters resting on a 

 sandy bottom and that they are not only firm enough to resist 

 the pressure of the current, but sufhciently impermeable to bank 

 up the water We may add to these extracts a bit of Australian 

 experience extracted from evidence taken before the Commission. 

 Mr. A. K. Smith, referring to a saw-mill constructed for himself 

 in Victoria, says, " the mill was built by some Canadians, and 

 they formed a dam across a creek in the Dandenong ranges. 

 They made simply a timber frame in the bottom, and when I 

 looked at it I had an idea that it would not be tight, because 

 there was nothing at the back, a,nd the fall was considerable. 

 But the creek brought down something which made a deposit, 

 and the dam became perfectly tight." 



It may be said that though percolation in the dam I propose 

 at Sans Souci miyht be practically innocuous so long as the fresh 

 water is kept above the level of the salt, that yet 1 am bound to 

 forecast the possibility of a case in which a long drought will have 

 emptied the reservoir, and the salt water will be pressing against 

 the outer side of the dam. What will then be the state of the 

 case ? Will not the salt water then ooze through ? To this I 

 reply first : it is extremely improbable that such a contingency 

 could arise. The tributaries to the George's Eiver have never 

 yet been known to cease running even in the driest season. The 

 Commit^siuners measured the delivery from the Woronora, and 

 found it, in a moderately dry period, delivering half a million 



