166. On the Sections of the Delta of the Yarra, 



to the Commissioners and the chief engineer of the Mel- 

 bourne Harbour Trust for permission to make use of the 

 data of precision, the plans and borings, prepared for the 

 construction of the canal; and I must also make my 

 acknowledgments to Mr. Davies and Mr. Meldrum, of the 

 Trust, who have given me very ready and intelligent assist- 

 ance in the inquiry on the spot. 



The canal is 6000 feet in length. It forms a curve, with 

 6000 feet as its shortest radius, trending nearly east and 

 west, and roughly conformable to the north shore of Hobson's 

 Bay. The average distance from the Bay is 7200 feet across 

 the Sandridge flats ; the west end of the canal is 4600 feet 

 below the confluence of the Saltwater and Yarra, and 

 12,600 feet from the sea extremity of the stone walls, 

 both measurements being taken along the present water- 

 courses. The width of the canal at low-water is 260 feet, 

 and the depth of the exposed excavation prior to the 

 dredgings 20 feet below low-water mark. I may say that 

 there is no appreciable difl'erence between the level of low- 

 water in the Bay and at Falls Bridge. The surface of the 

 ground being about 7 J feet above low- water, the total 

 vertical depth of the sections exposed was 27 feet; at one 

 point the depth reached 31 feet. 



Throughout the canal the appearance and sequence of 

 the beds excavated are as follows : — The floor and the 

 lowest part of the walls to a height of 4 feet on the 

 average consist of a stiff" yellowish clay, in which no traces 

 of life have been detected. The greater part of the side 

 walls is formed of a compacted, fine-grained black silt, having 

 an average thickness of 7 feet. Above the silt is a 

 capping of sand, with an average thickness of 16J feet, and 

 reaching to the surface. Both silt and sand contain marine 

 shells. The sections are fairly uniform from end to end of 

 the canal, though the silt drops from 8 feet to 5 feet from W. 

 to E. Only in one notable depression, to be dwelt on at a later 

 stage, does the silt dip below the floor of the cutting, and in 

 no case does it come within 13 feet of the surface of the 

 ground. 



The upper surface of the very stiff" yellowish clay, as 

 shown in the face of the sides, is roughly horizontal with 

 irregular undulations, whose amplitude never exceeds 3 feet. 

 There is but one marked inequality in the general level, the 

 exceptional depression referred to. The hollow is filled with 

 silt, continuous in bedding with the main mass. The 



