59 
mediate : while in the Tomkinson Ranges members of the 
basic and intermediate families are typical. The intermediate 
group is represented throughout by numerous diorite dykes, 
which are usually of no great thickness, but their frequent 
appearance within short distances of one another is in 
cases marked. Their plane of contact with the intruded 
rock is always well defined.* The diorite intrusions have 
occurred later than the main granitic injections of the dis- 
trict. This is evident from the fact that often the diorite 
can be found penetrating the granite, f Yet the diorite in 
places does not appear to have been much subsequent in time, 
for magmatic intergrowths may be observed between diorite 
and granite rock that have been produced during a state of 
semi-plasticity of the latter. On the other hand, magmatic 
inclusions of granite rock within the diorite occur. These 
have been torn from the walls of the fissure, into which the 
diorite was injected, and embedded in the mass. 
The intruded rocks, where they appear in considerable 
and persistent thickness (Mdchfigkeit ) , may be included 
generally under the headings of '"gneissic quartzite" % ^^ 
"gneiss" proper : yet other crystalline schists are not wanting, 
although they are not represented to the same extent. The 
great variations in readings of the compass needle, produced 
by the magnetic minerals contained in the different granitic 
rocks that compose these ranges, have already been noted by 
various explorers. 
The Musgrave Ranges. 
Genei^al Remarks. — The Musgrave Ranges (Gosse, 1873) 
lie almost wholly in the State of South Australia, only two 
minor offshoots passing northward to beyond the boundary, in 
the localities of Opparinna and Fraser Hill. They rise from 
the plains as a compact chain that continues in an easterly 
and westerly direction for a distance of over one hundred 
miles. They are, however, cut in several places by valleys of 
denudation that are now occupied by vast deposits of sand, 
the upper surfaces of which form elevated plains (such as 
Glen Ferdinand), that permit the ranges being crossed with 
no great difficulty transversely to their long axis. Their 
breadth varies, the maximum being about thirty-five miles, 
* Compare Michel-Levy. op. cit., pages 845 et 872, 
t See also H. Y. L. Brown. Report Journey from Warrina 
to Musgrave Ranges, page 2 (Adelaide: by authority. ISSO") : 
and Y, Streich, Scien, Res. Elder Expl, Exp., Trans. Roy. Soc. 
S.A., vol. xvi., pp. 77 and 83. 
t An altered (clastic) sandstone in which only a ver\' faint 
indication of foliation has been brought about by the proauction 
of secondarv minerals. 
