108 NOTES ON THE NEW HOB ART STORAGE RESERVOIR. 



The engineer, however, preferred to try the ground at a 

 lower level, and tunnels were driven from the bottom of the 

 shaft towards the JST.W. and S.E. respectively, for 45 feet 

 each way, the mudstone being continuous for that distance. 

 It is, perhaps, just as well that this mode of testing the 

 ground stopped where it did. Had the S.E. drive been con- 

 tinued for about 20 feet it would have broken into the fault, 

 and an additional element of insecurity would have been 

 imported into the affair. 



When matters had arrived at this stage the works were 

 suspended. When they were renewed in 1885, under the 

 management of the present Director of Waterworks, the open 

 cutting was extended, and, on cutting down to the rock at the 

 point which I had indicated, a vertical fault crossing 

 obliquely the line of excavation was clearly exposed. The 

 break in the rocks constituting the fault was about three feet 

 wide, with a well defined wall of mudstone on one side, and 

 of soft sandstone on the other, the remaining portion of the 

 cutting being through the latter rock. The fissure, instead 

 of being partly open, or loosely charged with angular frag- 

 ments of rock, as very commonly happens, proved fortunately 

 to be well and compactly filled with finely comminuted 

 material from the bounding rocks intermixed with vertical 

 bands of black clay. As a foundation for a properly laid 

 puddle wall it might be considered at least equal to that 

 afforded by the mudstone ; and though a better selection of 

 a site might easily have been made in the first instance, 

 there was no sufficient ground for incurring the large 

 additional expenditure that would have been entailed by 

 abandoning works on which so much money had been spent. 

 To describe the progress made from this stage with the 

 construction of the embankment and the other extensive 

 works connected with the formation of the reservoir, is for 

 the engineer rather than the geologist, and I believe that a 

 full account of the undertaking will be written by a more 

 competent hand than mine. Having had to criticise some- 

 what unfavourably the planning and construction of the old 

 Storage Eeservoir, I am glad to have an opportunity of 

 testifying to the sedulous care and skilful management with 

 which the physical difficulties of the situation have been met, 

 and which have set at rest all doubts that might otherwise 

 have been entertained as to the permanent success of this 

 important work. 



The excavations at the new reservoir have not added 

 anything new to the geological record. The so-called " mud- 

 stone " to which reference has been made is, in South- 

 Eastern Tasmania, the highest member of the Upper 

 Palaeozoic marine series, of which some representative beds are 



