1.38 
G. T. PRIOR. 
In the American quantitative system the rock would be classed as Auvergnose. 
The contact-effects produced in the dolerites intrusive in the sandstone and granite 
respectively are of interest. In each case the effects are similar, and due mainly to the 
sudden cooling. In place of a coarse-grained dolerite, the rock a few feet from the 
contact has the characters of a basalt, which becomes finer-grained and more glassy the 
closer it approaches the sandstone or granite ; at the same time the felspar and augite 
become long prismatic, with the former often enclosed in the latter (see Plate X, Fig. 3). 
At one or two inches from the contact the dolerite changes from black to a pale-green 
colour. That the production of this compact green aphanitic material is not due to any 
absorption of silica from the sandstone is shown by a determination of the silica in it, 
which gave a result 51 '96, actually lower than that obtained in the above analysis of 
the dolerite from Knob Head. 
In Plate X, Figs. 2-5 represent, as seen under the microscope, thin slices of 
specimens of dolerite collected at different distances from the contact with sandstone. 
Specimen 696 (Plate X, Fig. 2), from Dry Valleys, at 2ft. from the sandstone, still 
shows some augite in ophitic patches enclosing felspar- laths, but most of the pyroxene 
is in long prisms scattered through a base of felspar-laths, with interstitial felsitic 
material crowded with magnetite in rod-like skeleton-crystals. 
Specimen 687 (Plate X, Fig. 3), from Inland Forts, at 6in. from the sandstone, 
shows long interlacing felspar-laths and colourless augite dispersed about them and 
sometimes enclosing them, with interstitial patches of brown glass, dense with magnetite 
in rods and grains. 
Specimen 695 (Plate X, Fig. 4), from Dry Valleys, at 2in. from the sandstone, 
shows a further stage in the passage to a glass. The rock is variolitic, and much finer- 
grained than the preceding ; it shows a few porphyritic felspars, but consists mainly 
of radiating sheaves of felspar-needles, with interstitial glass dense with magnetite. 
Finally, at the actual junction with the sandstone, the rock (specimen 669, from B,) 
is a pale-brown glass with dark-brown clouded patches arranged in wavy lines roughly 
parallel to the line of contact (Plate X, Fig. 5). Close to the junction the magnetite is 
in feathery tuffs surrounded by clearer halos, but at a few millimetres distance it occurs 
in more distinct grains ; here also are seen one or two small porphyritic felspars and 
altered augites in a base which is confusedly crystalline, with radiating sheaves of 
minute felspar-needles, as in the preceding specimen but on a finer scale. 
Specimens from the contact of dolerite and granite at D 2 in the Kukri Hills show 
similar characters, except that in this case the chilling process has not proceeded so far. 
Thus specimen 705 shows, at the actual junction, no glass, but exhibits characters 
intermediate between those of specimens 687 (Plate X, Fig. 3) and 695 (Plate X, 
Fig. 4). 
The dolerite (119) from Granite Harbour has the same characters as those of the 
dolerites of the Ferrar Glacier, and shows similar patches of acid material. Specimen 154 
from this locality is a peculiar hybrid rock. It is a dark dolerite with numerous small 
