Vol. 6o.] OF THE EAST-CENTRAL HIGHLANDS. 417 



portioDs of this band niicrocline is even more abundant, the 

 principal accompaniments being green mica and granular sphene. 



The Dark Schist occurs as discontinuous patches that lie next the 

 Limestone, and between it and the ' Pink Felspathic ' material, when 

 both are present. These dark patches have proved of exceptional 

 importance, and will be discussed later on. 



The Limestone varies greatly in composition. As a rule, however. 

 it contains some suow-white, coarsely-crystalline calcite, and this 

 mav be present in separate thin' bands or mixed with other 

 minerals. In no case does this rock possess the grey coloration of 

 the typical Blair-Atholl Limestone and the Loch-Tay Limestone. 

 One of the thicker exposures (10,526) contains abundant epidote 

 and microcline. the latter mineral identical with that of the Piuk 

 Felspathic Rock, and a small quantity of either optically-anomalous 

 garnet or idocrase. In one place the calcareous material is obviously 

 mixed with a pink felspar, forming a coarsely-mottled pink-and- 

 green rock. The green mineral is malaeolite, and the pink the 

 typical microcline. 



At the junction of the tough Dark Schist with the base of the 

 limestone occurs a finely-banded rock. The paler bands are com- 

 posed of abundant epidote and zoisite, with a smaller quantity of 

 hornblende and calcite. The darker films were more aluminous 

 originally, and are now composed of plagioclase and quartz, 

 associated with chlorite and biotite. There are small spots in this 

 part of the rock, dusted over with minute biotite-flecks, exactly as 

 in a typical hornfels. 



It is thus apparent that the Limestone has not always the same 

 rock at its margin, and does not always rest upon the Moine Gneiss; 

 and there is clear evidence of a slight local erosion, or a small 

 hiatus in the succession. 



After a thorough investigation of the section below the Bridge, 

 the section above it may be examined. The rather massive and 

 highly-crystalline Moine Gneisses occupy the bed of the stream, 1 

 but the Limestone lies in the bank above, and its base is ex- 

 posed in places, while at the mouth of the little burn at the northern 

 end of Dalginross Wood, both the felspathic rock and the 

 Limestone are seen. At the base of the latter is a finely-banded, 

 markedly-fissile rock. This fissility is due to the perfect parallelism 

 of a large number of pale-brown micas, associated with a small 

 quantity of actinolite. The rock is structurally a fine quartz- 

 f elspar-biotite-granulite, with a considerable amount of 

 microcline, and a little carbonate and granular sphene (10, 52S). It 

 is of considerable importance, as suggesting a passage to the 

 felspathic material, and recalling the rock at Dalnacardoch and 

 the Gaick Burn. 



A few yards farther up the main stream the Pink Rock is seen 

 again in contact with the Moine Gneisses, and continues in this 



1 See fig. 2, p. 404. For the photographs, from which this figure and 

 figs. 3& 5 are reproduced, I am greatly indebted to Mr. Lunn, of the Geological 

 Survev. 



