460 
MR. D. SHARPE ON THE ARRANGEMENT OF THE FOLIATION AND 
clay lining each side, and a mass of calcareous spar down the centre. The annexed 
diagram, fig. 6, will give an idea of the appearance on the cliff. 
Fig. 6. 
h b. Hardened portion of the sandstone, deprived of the minor traces of stratification, 
c c. Sandstone close to the walls of the fissure vertically laminated. 
F F. The fissure filled with calcareous spar and clay. 
The changes which have taken place near the fissure are identical with those de- 
scribed by Mr. Hunt (49 and 51), the mass of the rock being laminated on the one 
part and rendered more solid on the other, which we may safely conclude to have 
been produced by galvanic currents passing between the mass filling up the fissure 
and the body of the rock on each side ; but it would be too bold a speculation which 
should attempt to explain the regular cleavage of whole formations of slate by com- 
paring it to the trifling change described above. 
Explanation of the Map and Sections, Plates XXIII., XXIV. 
As the object of the Map is to represent the direction of the foliation and cleavage, 
the geological features which have no reference to that subject have been kept as 
little prominent as possible, and only as many colours employed as were indispensable. 
The whole of the foliated rocks are painted of one yellow colour, which thus includes 
gneiss, mica schist, chlorite schist, hornblende schist, and the gneissose quartz rock. 
The stratified slates are coloured purple. The brown colour includes the Old Red 
Sandstone, the stratified quartz rock and the limestones associated with them. The 
more modern formations, which cover a very small space in the Highlands, are 
omitted. Granite, syenite and the older porphyries are coloured pink, and the more 
modern trap-rocks red. Thus two colours, the yellow and purple, represent the rocks 
affected by the foliation and cleavage ; the pink includes all the plutonic rocks which 
have broken through and disturbed the foliation and cleavage ; the brown and red re- 
present the rocks which overlie and conceal the rocks affected by those phenomena. 
The strike or direction of the foliation and cleavage across the surface is indicated 
by black lines ; when these are double the foliation or cleavage is vertical ; a single 
