Victorian Igneous Rocks. 285 



The four analyses have been recalculated to 100 per cent., as in 

 the case of previous analyses, and the results, together with tlie 

 molecular ratios, are given in Table XV. 



Total - 100.00 1.543 100.00 1.528 10<J.(K) 1.527 100.00 1.551 



It is found that these analyses do not conform to the lines of 

 variation of the dacite-granitic series, as shown in Fig. 3, or in the 

 generalised diagram, Fig. 4. The unit molecular concentrations 

 of three of the rocks show distinct departures from the mean 

 concentration of the dacite-granitic series, viz., 1.541. In the case 

 of the Macedon alkali rocks it has been seen that those rocks whose 

 unit concentration departed from the normal variation for the 

 series Avere probably derived by complementary differentiation. 

 This suggests the possibility that these Lilydale rocks may have been 

 produced by a similar form of differentiation. In this case there 

 is an absence of quantitative data such as was available in the case 

 of the Macedon rocks, and so no direct method is available for 

 determining the relative proportions of the rocks. It is possible 

 that an approximation to the truth may be obtained by combining 

 the analyses in such proportions that the total molecular ratios of 

 the resultant composition may be about equal to the mean molecular 

 concentration of the granite dacites series, viz.. 1.541. This result 

 will be obtained by combining the analyses in the proportion of one 

 part of each of the Analyses I., II. and III., and two parts of 

 Analyses IV. One part each of Analyses I. and III., and two- 

 parts of Analyses II., and three parts of Analyses IV. will also give 

 approximately the same molecular total. 



