part 3] MINERALS IN COBAL- LIMESTONES OF BABBADOS. 10T 



and also many specimens of low-level beach-rock. Sir Francis 

 Watts, K.C.M.G., Imperial Commissioner of Agriculture for the 

 West Indies, in addition obtained for me large samples of reef- 

 corals and of beach-rock l from the higher coralline limestones of 

 Barbados. Great care was taken to ensure that the specimens 

 were collected from positions where they could not possibly have 

 been contaminated by the 1812, 1902, or 1903 falls of volcanic- 

 ash ; while I took samples for examination of the corals and of the 

 beach-rock from the interior of the specimens, so as to make quite 

 certain that no contamination could have occurred in them. 

 Quantities of 1000 grams of each were dissolved in dilute hydro- 

 chloric acid, and the residues collected for further examination. Ir» 

 work with Barbados rocks in 1888 and 1889 I found that very 

 dilute, approximately deci-normal, cold hydrochloric acid has no 

 greater solvent effect on the earthy or clayey constituents of lime- 

 stone than has dilute aeetie aeid. 



The method used was to support the fragments of limestone in 

 a perforated shallow porcelain filtering-dish immersed just below 

 the surface of several litres of the diluted acid which, as neutralized 

 by solution of the calcium carbonate of the rock, received additions 

 of hydrochloric acid in small quantities at a time, so as to keep 

 the liquid at approximately its original degree of acidity. As the- 

 limestone slowly dissolved, its insoluble constituents gradually sub- 

 sided to the bottom of the diluted acid. After complete solution 

 of the rock was effected, the liquid was allowed to stand until it 

 had become quite clear through the sedimentation of the insoluble 

 residua. The liquid was decanted off, and the sediment Avashed 

 with distilled water by subsidence and decantation until the acid 

 was almost all removed. The insoluble matter was then decanted 

 into a large, porous, alundum (fused alumina ) liltering-cone, and 

 drained. The residue was washed on the cone with distilled water 

 until all soluble matter was removed. It was next washed off the 

 interior of the cone by a jet of distilled water into a tared platinum 

 basin, in which it was dried at 105° C, and weighed. The dried 

 residua were then analysed both chemically and microscopically by 

 well-known standard methods for such work. Excellent samples 

 of corals and of beach-rock from the following localities were thus 

 examined : — 



Corals. Beach-Rock. 



Altitude Locality. Altitude 



Locality. in feet. infect. 



Mount Misery (re-ci'ystal- ") , . .. Bloomsbury about 1035 



lized or calcitized coral) . ) :1 " ut ' ' Mount Wilton „ s>37 



Bloomsbury ., 1036 Blackmails.. „ 900 



Blackmans „ 900 Low-levels, Franks'scollec- 7 QntnSnO 



Dunscorabe „ 850 ; tion — various localities... ) 



Vaucluse ., 731 



Low levels, Franks's collec- 

 tion — various localities ... 



30 to 250 



1 In these notes, under the term ' Beach-Book,' I include limestones made 

 up of reef-rocks and of channel- or lagoon-deposits, as well as actual beach- 

 rocks. 



