-i'3'5 



MB. 0. A. DEEBT OX 



the red rock at a low angle. The tunnel, which describes a strong 

 curve, soon enters wholly into the foyaite. which appears in the 

 floor, roof, and sides ; but a few metres beyond, the red rock appears 

 again irregularly, still rising highest on the left side when the 

 exposure is continuous (3 ), while in front it is divided into three 

 distinct masses, the foyaite sinking between to below the floor of the 

 tunnel (4). The road-bed again rises above the level of the lower 



Fig. 4. — Sections across and on the sides of tJie tunnel near Pinlialzialw. 



- * * * JL* * * " * 



1 .. X 



a. Fovaite. 



b. Red rock. 



1. Upper mouth of tunnel. 



2. Lower mouth of tunnel. 



3. Left side of tunnel near upper end. 



4. Eight side of tunnel near upper end. 



contact of the foyaite and the red rock, and continues in the former 

 to the lower opening, where the latter again appears in very small 

 patches on each side, which only rise very slightly above the floors. 

 The foyaite forms quite a regular arch over the lower mouth of the 

 tunnel (2) ; this comes out at the upper surface of the mass, which is 

 covered completely by the red rock. The latter is here so broken into 

 small fragments as to resemble an immense heap of chestnuts, and a 

 land-slide of this incoherent material had. at the time of my visit, 

 revealed a considerable surface of the foyaite on the slorje over the 

 mouth of the tunnel. This contact-surface was irregularly undu- 

 lated, and inclined at an angle of 15 c — 20°. The rock-openings and 

 a part of the interior contacts have been concealed by masonry, but 

 a portion of the latter are still exposed. 



Both rocks near the contact are generally decomposed, and the 

 red rock is everywhere too much so to reveal any modifications that 

 it may have suffered. In places, however, the foyaite shows an in- 

 teresting contact-phenomenon. At about a metre away the rock 

 becomes finer-grained, and passes rapidly into foyaite porphyry and 

 finallv into true phonolite. the phonoiitic facies extending for 10-15 



