280 DISCUSSION, 
Mr. Smith—“ That authentic rubies do exist in the neighbour- 
hood of Mudgee is undoubted ; in Mr. Stephen’s collection some 
specimens from that locality were determined by myself.” 
Reply—This is a plain statement of fact, but it is also true that 
twenty-six years ago Prof..Thomson found rubies at Two Mile 
Flat, near Mudgee, and actually published an analysis of them,” 
and to him therefore is due the credit of first determining “that 
authentic rubies exist in the neighbourhood of Mudgee.” 
Mr. Smith—* From the figures therein given it is not possible 
to obtain the theoretical formula for topaz.” 
Reply—tThat is so obvious as to render discussion unnecessary. 
Divergences of the sort are found in the work of some of the most 
eminent analysts.” 
Mr. Smith—‘‘When differences of three or four per cent. are 
obtained it is better that the analysis should not be published.” 
Reply—This statement is an expression of opinion only—an 
opinion with which I cannot agree. As opposed to it, it may be 
noticed that Genth, Wachtmeister, Delesse, and Liversidge have 
published analyses where “ differences of three and four per cent. 
are obtained.” For example in Vol. xx1x., p. 324 of this Society, 
just issued, Professor Liversidge gives an analysis of topaz from 
Shoalhaven, which differs more than three or four per cent. from 
theoretical requirements. Here are the figures— 
Analysis of Topaz. 
My results Theoretical requirements. Prof. Liversidge. 
SiO, 30°29 sea 35°3 Ae 28°19 
AlO, 60-90 “ 56°5 ae 62°66 
CaO “40 
F 15-05 17°6 : 14-01 
Tam content to follow in the footsteps of analysts, whose scholar- 
ship and technical skill is beyond dispute, and consequently venture 
to publish my analysis, notwithstanding Mr. Smith's declaration 
that this “should” not be done. 
a 
* Traas. Roy. Soc. N. S. Wales, 1870, p. 191. 
