116 WATER SUPPLY TO SYDNEY BY GRAVITATION. 



inner part of the pipes at the time of the construction of the same. 

 Wrought-iron mains of 4-lGth of an inch thick, if not properly 

 protected when under use for water conduit, would corrode 

 through in about fifteen to twenty years even without pressure, 

 whilst with pressure, such as my scheme would impart, the pipes 

 would probably become worthless in less than ten years. I would 

 therefore advocate enamelling from the first for the inner coating, 

 whilst the outside could be perfectly protected by an annual 

 painting over with inferior residue oils from the kerosene works. 



I have before stated that my scheme embraces no attempt at 

 any system of irrigation, because it is quite impossible to supply 

 waters for such purposes cheap enough, where iron pipes are 

 necessary for the conduit of the waters. If irrigation can be made 

 use of for the county of Cumberland in this Colony, it can only 

 be by the very costly and dangerous erections of immense dams 

 to throw back almost inexhaustible supplies of flood waters, in 

 manner as has been undertaken lately at Poonah in India, and at 

 Eurens by St. Etienne, in France, both built in solid masonry 

 bedded with liquid cement. 



By my scheme, and along either the high or the low level 

 gathering-grounds, I am satisfied that very vast bodies of 

 water, even for extensive irrigation, could be obtained and im- 

 pounded by means of the erection of high dams. But cat bono / 

 When such supplies could not be conducted to arable or pastoral 

 lands without the application of expensive iron mains, or by cir- 

 cuitous and very long open channels, that would never repay 

 interest on the cost. 



But even if the expenses were not alone a sufficient drawback 

 to the erection of high enbankments for such purposes, I have 

 gathered sufficient information on this subject to deter me from 

 like advocacies. In the report on the " Ballarat Water Supply 

 Extension," drawn up by Mr. G\ Gordon, the able Engineer-iu- 

 Chief for Victoria (and who was sent down from Madras under 

 the recommendations of Colonel Sankey, an equally talented 

 hydraulic engineer), I observe some valuable remarks on the sub- 

 ject of high enbankments, which I will here quote. At paragraph 

 15 he says — " It will not, I think, be denied that there is con- 

 siderable risk attending the construction of large embanked 

 reservoirs. Although there is no difficulty in designing a bank 

 which will theoretically be able to retain 100 or even 200 feet of 

 water, the risks of failure increase in a greater ratio than the 

 square of the height. It is no disparagement of the skill of any 

 engineer to state that fact, nor will any one who has experience iu 

 making high dams be inclined to make light of it." Mr. Gordon, 

 in support of these view r s of his own, quotes several apt passages 

 from evidence given before a Committee of the House of Com- 



