92 Armitage, Country about West Essendon. [ Sept '" 



to the hills and lying on formations up to Cretaceous in 

 age (17). 



The only Tertiary quartzites referred to by Mr. R. A. F. 

 Murray (18) as being found in Victoria are those which " have 

 been found to be clearly antecedent to the Older Volcanic rocks." 

 He makes no mention of any quartzite found above the Older 

 Volcanic. Messrs. Hall and Pritchard (19) discuss a mass of 

 90 feet of quartzites near Maude, which occur beneath the 

 Older Volcanic, and mention younger beds at Keilor, beneath 

 the Newer Volcanic basalts. Quartzite and greywacke in beds 

 of pre-Newer Volcanic age occur not only at West Essendon, 

 but at many other localities in the vicinity of Melbourne. 

 In all cases they occur as patches of variable area, and often 

 quite close to sediments which show, as a rule, very little 

 cementation. To account for this erratic manner of occurrence, 

 it has been suggested that alkaline waters draining along and 

 through portions of the Newer Basalt have caused the solution 

 of silica, which has become re-deposited as a siliceous cement 

 amongst the quartz grains of the beds, firmly binding them 

 together. But in many localities where water is seen freely to 

 pass into the underlying sands after percolation down through 

 the overlying basalt, such sands are found to be almost as little 

 bound together as the sands of the seashore. This may be 

 noticed, for example, in the ancient river sands under the basalt 

 of both the Clifton Hill and Burnley quarries, as well as in the 

 sands under the basalt at North Coburg. Such an explanation 

 for the silicification does not seem to be satisfactory. 



Messrs. Irving and Van Hise refer to this idea in connection 

 with the formation of silicified sediments in Wisconsin, of 

 which they write (20) : — " These greywackes .... occur 

 interstratified in a great thickness of unaltered sandstones. 

 Moreover, they lie ... . many hundred feet above the 

 latest of the great flows of eruptive material, .... so that 

 the alteration can in no way be attributed to igneous action." 

 While, as far as is known, our pre-Newer Basaltic quartzites are 

 closely associated with the presence of overlying basalt, their 

 cementation need not necessarily be due to that fact. It is well 

 known that the last stages of vulcanicity are characterized by the 

 welling-up of hot springs of mineral water, as well as by emana- 

 tions of gases from below. In parts of Victoria mineral springs 

 still exist, many of which may be regarded as representing the 

 very latest dying stages in the volcanic activity of the districts 

 where they are found. The Hepburn Springs, near Daylesford, 

 and the Drysdale Springs may be cited as examples, the water in 

 the former being highly carbonated as well as bearing other 

 ingredients, while that of the latter is charged with sulphuretted 

 hydrogen. It may be mentioned that a spring exists in the cliff- 



