SKY. GEOLOGY. SECONDARY STRATA. 325 



nicer transition from the stratified to the unstratified 

 limestone, immediately below the syenite of Ben na 

 Charn ; the beds lying in the usual position and containing 

 the shells already mentioned, but the rock itself being 

 of a crystalline character, and weathering into that very 

 singular honeycombed, or spicular and ridgy form which, 

 with its durability and hostility to vegetation, distin- 

 guishes so strongly the stratified from the unstratified rock. 



The last affinity between the two which I shall here 

 notice, is the occurrence of substances in the unstratified 

 rock, so nearly resembling those ranked under the general 

 term of alcyonium, that it is probable they owe their 

 origin to organized bodies. They are occasionally dis- 

 posed in an irregular manner, but in some places form 

 layers in the rock as distinct as those by which the 

 flints of chalk are characterized. They consist of a 

 calcareous carbonate, whiter and harder than the sur- 

 rounding rock, and are covered with minute crystals 

 of the same substance, of a peculiarly brilliant aspect. 

 Their superior permanence causes them to protrude long 

 after the including mass has wasted away, and they 

 can thus be easily procured in an entire and separate 

 state. In a few instances they are found broken into 

 two parts and reunited by intervening limestone, without 

 any material disturbance of the separated portions. The 

 occurrence of the rare and beautiful Dryas octopetala 

 in great profusion, will guide the geologist to this rock, 

 which might otherwise escape his observation. 



Before quitting this part of Strath I must mention 

 a substance connected with the limestone, because it can 

 no where else so well find a place, and is not sufficiently 

 extensive or important to require a separate consideration. 

 This is a calcareous conglomerate, occupying a portion 

 of the hill next to the syenite so often mentioned ; but 

 its connexions cannot be traced. That however is of 

 little moment, as the occurrence of similar conglomerates 



