102 WATER SUPPLY TO SYDNEY BY GRAVITATION. 



entirely new river in a northerly direction to connect with my 

 present proposed channel to be led on through the Loddon tunnel 

 to the high gravitation mains, and thus insure to the future 

 Sydney an unparallelled water supply by high gravitation. 



I must now proceed to give an account of my survey made in 

 the months of February and March last, and followed in May 

 and June by subsequent aneroid observations taken in three sep- 

 arate trips to Illawarra. I began my second survey by measur- 

 ing off the true levels, at the proposed dam, 'at elevations on both 

 sides of the Loddon River of 50 feet. I then started the levels 

 and the traversing from the eastern peg of the dam at its intended 

 overflow over a ridge into another creek close at hand. We 

 maintained that exact level all round the various valleys which 

 debouche into the Loddon Eiver, until after surveying round for 

 seven miles and three-quarters, under six days' work, we had the 

 gratification to find that our workings with the instruments had 

 been so very correct that, on our approaching the western side of 

 the dam, and when we thought that we were still some distance 

 away from it, we found that our sights for the true levelling had 

 been so correct that our last sight with the instrument cut the 

 ground at only six inches above the western peg of our first 50-feet 

 level for the dam itself from the corresponding point on the 

 eastern side, from whence we started. 



I mention this interesting fact as a proof of tbe correctness of 

 the survey, and of the true taking of all our elevations everywhere, 

 from the sea level up, and which reflects great credit upon my 

 young assistant in the survey, Mr. Carl Weber, who worked the 

 instrument and kept the field book. 



My new map, which embraces all the late survey work done in 

 February and March, as well as that of the first survey in October 

 of last year, shows the proposed impounding of 366 acres of water 

 by the intended " Lake Loddon," whilst the soundings of such 

 contemplated deep water lake are shown sufficiently on the face 

 of the map, in feet, to enable you to have some idea of the vastness 

 of the supply for Sydney, which can be so readily and safely im- 

 pounded there by the formation of one fine dam, with 50 feet 

 elevation only, to be made in cement concrete, from broken road- 

 stone, sand, and Portland cement and water, as proposed in my 

 former paper. 



The estimate of the contents of the lake is based on a calculation 

 of the cube of the depths, and by taking 6£ acres at 6 feet deep 

 to represent ten million gallons of water, whilst by averaging the 

 depths of the soundings (without cross sections being taken) we 

 arrived at the estimate of 2,000 million gallons of storage waters, 

 or nearly four times as much storage capacity as all the Lachlan 

 Swamp and Botany dams put together would represent. It is 

 difficult to convey to the mind of those who have not seen the 



