HONEYMAN ON THE METAMORPHISM OF KOCKS. 2SS 



an eminence — red, prominent, and visible at a c;reat distance, form- 

 ing a land mark. At the north of this, and in contrast with it, is 

 porphyritic and amygdaloidal trap, which have parcellanized the 

 arenaceous strata, bnt only in such a degree as to render them 

 readily fissile. 



On the north-west, the same strata, forming part of the pier, are 

 in contact with the massive trap already referred to, and have con- 

 sequently been hardened in an extreme measure. The massive 

 rock is jaspideous and uncleavable, being generally uniform, some- 

 times beautifully banded, and reticulated with veins of quartz and 

 sulphate of baryta. The l^oulders of this rock rolling on the 

 shore, when washed by the sea, are beautiful and varied ; they are 

 as hard as quartz, and susceptible of a high polish. The French- 

 man's barn is another part of the same band. I have observed that 

 the trap lies in the sea on the north of this rock. The north side 

 of the rock is a wall washed by the sea. This is an enormous mass 

 of jaspideous rock metamorphosed by the action of the trap. It is 

 also pervaded by quartz and sulphate of barj^ta veins. 



At Black Rock where the trap from the east first meets with the 

 Upper Arisaig strata, we have also the same lower band metamor- 

 phosed and converted into a very hard brown jaspideous rock. 

 Yv^hen broken this shows in cells, iron and copper pyrites, and 

 malachite. Connected with this I discovered in 1869 a soft rock 

 easily cut with a knife, and having a greasy touch. This rock is 

 of brown and variegated colour, and is susceptible of a fine polish. 

 When I found it, I believed it to be saponite, var. renssellaerite. 

 It is now believed to be a silicate of alumina, somewhat resembling 

 agalmatolite. The rock appears to be about twelve feet wide ; it 

 has the hard jaspideous rock below and above. The stratum ap- 

 pears to be lenticular. Its next appearance is a little to the east of 

 the Frenchman's barn : here it comes out of the sea. Its colours 

 are yellow, orange, and red ; specimens are very beautiful when 

 polished. It passes on the south side of the Frenchman's barn, 

 where it appears as a shaly rock, having singularly granular 

 nodules, which give it the appearance of conglomerate. Farther 

 west from the barn, the rock under notice has its maximum thick- 

 ness. Here it consists of mahogany coloured states, having the 



