1862.] SAWKINS GRANITE, JAMAICA. 35 



position to have been acted upon by water. The pink and cream- 

 coloured schists are situated within the limestone-basin, attaining an 

 elevation of 250 feet, the limestone forming a thin belt at the foot of 

 the hill, on the north, south, and west sides. That on the east side 

 occupies a higher position, and at the north-east corner of the basin 

 graduates in step-like terraces, till it joins, or nearly joins, the lime- 

 stone at the foot on the south side. The area of this limestone-basin 

 is not less than 40,000 square yards ; but outside it three other rocks 

 are seen, the highest being a silver-grey, micaceous schist ; secondly, 

 a sandy, brown-coloured schist ; and, thirdly, a hard, massive, blue 

 schist, with innumerable circular impressions. 



4. On the Association of Granite with the Tertiary Strata near 

 Kingston, Jamaica. By J. G. Sawkins, Esq., F.G.S. 



[In a letter to Sir R. I. Murchison, G.C. St.S., F.R.S., F.G.S., &e. Dated 

 t Kingston, July 29th, 1862.] 



The object of my writing at present is to inform you that, during 

 the last few months, I have been tracing out a very interesting 

 granitic formation traversing this island from the S.E. to the N.W., 

 the direction of our earthquake-shocks. 



My interest in the investigation was enhanced because it was 

 generally supposed that lower rocks of this intrusive class did not 

 appear on this island, and also by frequently observing small crystals 

 of the carbonate of copper associated with it, by which I was 

 encouraged in the belief that I should find this metal accompanying 

 the granitic formation. 



This formation first appears in the parish of Port Eoyal, piercing 

 through the carbonaceous series ; then west of the Hope River, in 

 the parish of St. Andrew, between the white limestone and con- 

 glomerates. It is consequently of Tertiary age. It sinks below 

 the white limestone at Stony Hill, rises again through the same 

 to the N.W., and trends off into the parish of Metcalfe, where I found 

 the copper associated with the granitic series in the manner the 

 specimens sent with this note will illustrate, which I consider an 

 interesting fact to lay before you. 



The character of the granitic rock differs materially in the quantity 

 of each constituent, and it is more frequently accompanied with 

 hornblende than mica, the amount of felspar being greater than 

 the quartz. It has, in many instances, undergone decomposition to 

 so great an extent that it is recognized with difficulty. 



After I surveyed Anguilla, some of the Americans engaged at Tom- 

 brero examined and experimented on the bone-breccia I found there ; 

 they abandoned it in a few days, and found no phosphatic rocks on 

 the island worthy their attention. 



d2 



