40 



No. 5. 



Carbonate of liine, 31*94 



Insoluble siliceous matter, 68*06 



100-00 



It appears from these analyses, 1. That the cornstones of Innerkip 

 are carbonates of lime and not dolomites. 



2. That in this locality igneous action has converted a carbonate 

 of lime into a bisilicate. Now, as it appears from analyses 1 and 2 

 that there is but a trace of siliceous matter in the limestone, the 

 origin of the silica must be sought in the igneous rock ; in fact, a 

 transference of a portion of its silica must have taken place when the 

 basalt was in a state of fusion. Such transfer, indeed, could readily 

 take place under the influence of chemical attractions, when the rocks 

 were in a state of even imperfect fusion. On No. 4, or the table 

 spar, Dr. E. D. Thomson remarks : 



" It is an interesting fact in connection with this mineral, that it 

 gives a yellow colour before the blowpipe when moistened with 

 muriatic acid ; and yields crystals of common salt when treated with 

 the same acid. It is thus associated with Wollastonite, or soda table 

 spar, a mineral occurring in the Bishopton tunnel, and in the Kil- 

 patrick Hills." There is, however, this difference between the two 

 cases, that in the localities last mentioned the mineral has no direct 

 connection with limestone, although calcareous spar occurs abun- 

 dantly ; whereas at Innerkip, it has obviously originated in a change 

 induced upon common limestone. 



VI. THE OLD SLATES. 



29. These rocks are portions of the great bands of sedimentary strata 

 which traverse Scotland from sea to sea, in a direction parallel to the 

 principal axis of the Grampians, and to the great Caledonian valley. 

 They first strike the shores of the Clyde a little to the east of 

 Kilcreggan pier in Porthill Bay, where the junction with the old 

 red sandstone is concealed as already mentioned. They deviate very 

 little from their ordinary type, and it is therefore unnecessary to 

 enter into any lengthened descriptions. The usual varieties, depend- 

 ing upon the varying proportions of the constituent minerals, occur 

 abundantly, but in no definite order, and without much continuity. 

 Thus the clay slate series exhibits beds of flinty slate often approach- 

 ing to quartz rock, of highly bituminous slate, and of coarse grained 

 compact thick bedded slate, mixed up irregularly with the commoner 

 kinds, such as coarse and fine roofing slates, and a semi-crystalline 



