by h. i. jensen. 621 



Discussion of the Analyses. 



The chemical analyses appearing in Table i., with the exception 

 of those which are inserted for comparison (A to E), were 

 carried out by myself in the research laboratory of tlie Chemical 

 Department, Sydney University; and I desire to express my 

 thanks to Professor Liversidge, M.A., F. R.S., etc., and Mr. 

 Schofield, A -bl.S.M,, for putting at my disposal the apparatus 

 necessary. 



The exigencies of time did not permit me to make duplicate 

 analyses. Though several of my analyses sum up below or above 

 the limits of first-class work, none of them are so inferior as not 

 to be useful for comparison. 



The reader is recommended to compare the composition of the 

 Warrumbungle Mountain rocks with the analyses of the trachytes 

 from the Glass House Mountains, Q.,*from Mittagong, N.S.W.,t 

 from the Mount Macedon district, Victoria, | and from the Otago 

 Peninsula.^ 



Special Notes. 



W.67. This rock was analysed to verify chemically the con- 

 clusion arrived at by microscopic examination, that this orthoclase 

 basalt and the trachydolerites allied to it (e.g., W.64) were formed 

 by a mixture of magmas. The CaO and MgO are too low and 

 the alkalies (especially KoO) are too high to permit the rock to 

 be referred to the basalts. Nor can it be referred to the trachy- 

 dolerites, as the AI0O3 percentage is too low. The alkaline 

 basalt from the Blow Hole Flow near Iviama|! is closer to it in 

 chemical composition than any other rock of basaltic appearance 

 of which I can find analytical records. The norm is that of 

 "akerose." The rocks which usually have this composition, 



• H. I. Jensen, These Proceedings, 1906, Part i. 



t D. Mawson, Journ. Proc. Roy. Soc. N. S. Wales, Vol. xxxvii. 



+ Quoted by Prof. Gregory, Proc. Roy. Soc. Victoria, Vol. xiv., Pt.2. 



§ P. Marshall, 'The Geology of Dunedin,' Q.J.G.S., Vol. Ixii., 1906. 



II 'Geology of the Kiania-Jamberoo District,' Records Geol. Surv. N. S, 



Wales, Vol.viii., Pt.l. 



