158 PEOF. J. B. HARRISON OX EXTRANEOUS [vol. lxxv 



9. Notes on the Extraxeoes Minerals in the Coral-Lime- 

 stoxes of Barbados. By Prof. John Burchmore 

 Harrison, C.M.G., M.A., * F.G.S., F.I.C., assisted by 

 C. B. W. Axdersox, 3rd Assistant Analyst, Department of 

 Science & Agriculture, British Guiana. (Head June 25th, 

 1919.) 



During the investigations of the geological structure of Barbados 

 (British West Indies) in collaboration with the late A. J. Jukes- 

 Browne and the late G. F. Franks, in the years 1884 to 1893, the 

 results of which have appeared in a series of papers published in 

 this Journal, 1 a fairly complete examination of the coral-rocks of 

 that island was made. An earlier very accurate examination was 

 made by Sir Robert Schomburgk, and a good account of it was 

 given in his ' History of Barbados' (18-18). 



Schomburgk, as later we were, was struck with the occurrence 

 of numerous beds of volcanic ashes characterizing the Oceanic 

 Series of foraminiferal, radiolarian, and argillaceous deep-sea 

 deposits so well exposed in Barbados. In the series of Globigerina 

 Marls and Amphistegina Limestones and Basal Reef -Rocks, de- 

 scribed on pp. 212 to 217 of the 1892 paper and on pp. 510 to 549 

 of the 1898 paper, fairly abundant proofs of volcanic activity in 

 the Caribbean region during their deposition occur in the form 

 of fragments of volcanic glass, felspar, and occasionally, though 

 rarely, of pyroxene. But no observer found any beds of volcanic 

 ash, or even any indication of volcanic activity, in the strata 

 forming the coral-limestone terraces, the deposition of which 

 probably began in the Pliocene, and certainly continued to recent 

 geological times. 



In the 1891 paper I regarded the acid-insoluble residue of the 

 coral-rock, the analyses of which are given in that paper, as 

 consisting only of silica with clay, iron peroxide, and alumina, 

 these constituents varying from 017 to 3-10 and from 0*17 to 

 227 per cent, respectively. The analyses were all made on bulk- 

 samples representing the limestones, and any adherent or infiltrated 

 earthy matters contained in them. My original notes on the 

 analyses do not show that I determined the actual composition of 

 the fraction which I then termed ' silica and clay.' 



Mr. G. F. Franks died in 1917, bequeathing his collection 

 of rocks and rock-sections to me. On examination of his numerous 

 sections of coral-rock, I noticed that some of them showed the 

 presence of angular fragments of felspar, while I found but 



1 Q. J. G. S. vol. xlvii (1891) pp. 197-250 ; vol. xlviii (1892) pp. 170-226; 

 vol. li (1895) pp. 313-28; vol. liv (1898) pp. 540-55; and vol. lxiii (1907) 

 pp. 318-37. 



