268 PROCEEDINGS OF SECTION C.: 
— 
conspicuously from typical phonolites in the followin 
respects :—-(1) low silica percentage; (2) entire absence of 
phenocrysts of sanidine. It is obviously a felspathoid rock, 
and although its silica percentage allies it with the basalts, 
its mineral constitution, chemical composition, and low 
specific gravity link it with the phonolites. As far as the 
authors are aware, it is unlike any rock that has hitherto 
been described from any part of the world.”’* 
It is undoubtedly a rock of the foyaitic magma, and has 
no relation whatever with basalt. 
Take, again, the new theralitic rock Euctolite, described 
by Rosenbusch from Umbriat, It is an olivine-melilite- 
leucite rock allied to madupite, which is a biotiteleucite- 
diopside rock. Its SiO, per cent. is only 41-4, and would, 
if alone relied upon, indicate basaltic affinities, while its 
real relations are theralitic. 
SES the signs of a growing discontent with the existing 
empirical schemes of classification, the critical contributions of 
Professor F. Loewinson-Lessing are important.{ His guiding 
motto is, ‘chemical composition the basis of rock classifi- 
cation.” His application of it is less acceptable. He uses 
a dualistic nomenclature, referring to the felspar and the 
colored constituents. Thus, with respect to Syenite, he 
distinguishes Orthoclase Syenite, Albite Syenite, Anortho- 
clase Syenite; and secondly, Hornblende Syenite, Augite 
Syenite, Mica Syenite, Aegirine Syenite, &c. Then, com- 
bining both constituents, he adopts such terms as Orthoclase- 
hornblende Syenite, Anorthoclase-aegirine Syenite, &e. 
As will be seen later, I propose to avoid this dual termin- 
ology, by detaching the alkali granites and syenites from 
the normal series altogether. We shall then adopt the 
specific names which have been used for the different rocks 
of these groups, such as pulaskite, laurvikite, &c. 
The plan which I now venture to propose is to arrange 
the primary divisions in accordance with the rock-magmas 
assumed by H. Rosenbusch, and we shall then obtain the 
series, as under :— 
1. The Granite-Syenite-Diorite series ; 
2. The Gabbro-Peridotite series ; 
The Elzolite or Nepheline series of rocks. 
The sub-divisions, as they affect Tasmania, are represented 
in the attached scheme. For myself, I do not fear that this 
* Roy. Soc. N.S.W. Abstract of Proc., June 5, 1901. 
+ Ueber Euktolith, ein neues Glied der theralithischen 
Effusivmagmen. ; 
tVide Tschermak’s mineralogische u, petrographische Mitt- 
heilungen, 1900. 
