358 T. W. E. DAVID, F. B. GUTHRIE, AND W. G. WOOLNOUGH, 



over a mile in width ; and beyond it the granite extends to a 

 considerable distance further in a westerly direction. The eastern 

 line of junction between the granite and the phyllite trends N. 

 15° E. and S. 15° W., while the western junction line is nearly 

 meridional, so that there does not appear to be any relation 

 between the strike of the tinguaite dyke and the junction line 

 of the granite and phyllite. The same remark applies to the 

 junction line of the granite with the radiolarian and graptolitic 

 slates and cherts at twenty-nine miles in a direction E. 25° N. 

 from Kosciusko. The folia of the granite strike N. 20° E. to 

 N.N.E., and their prevalent dip is to E.S.E. at about 75°. The 

 granite is strongly intrusive into both phyllites and radiolarian 

 rocks. The age of the phyllites is unknown ; but that of the 

 latter is Lower Silurian (Ordovician). The tinguaite is strongly 

 intrusive into the gneissic granite, and contains a large amount 

 of included crystals of felspar, with a few of quartz and mica, 

 derived from the granite. 



An examination of the gneissic granite shows that it has been 

 intruded by at least two distinct dyke rocks, other than the 

 nephelinite, as well as by veins and irregular masses of a whitish 

 euritic granite. The last mentioned is probably not much younger 

 than the gneissic granite, as it has partaken of its foliation. The 

 two dyke rocks referred to are respectively a pyroxene araphibolite, 

 and an olivine basalt. 



The nearest basalt dyke to the tinguaite, as far as we were 

 able to observe, is one seen by us on the west side of Lake Mere- 

 wether (the Blue Lake). It is about two feet wide and strikes in 

 a direction from W.N.W. to W. 30° N. A much larger basalt 

 dyke is developed on the Main Dividing Ridge to the west of 

 Garrard's Tarn (Harnett's Lake, or Club Lake). This dyke is 

 several yards in width and is perhaps a continuation of the dyke 

 next to be described, viz., that at Russell's Tarn near Mount 

 Townsend (Muller's Peak). This dyke is forty yards wide, is 

 strongly laminated and strikes in an E.N.E. direction, whereas 

 the laminaB trend N.N.E. and S.S.W. This dyke is rendered 



