302 On the Cause of Induration of some Siliceous Sandstones. 



to both ; which are, I believe, the common cementing princi- 

 ples of the generality of sandstones, whether siliceous or cal- 

 careous. 



I may mention incidentally, as tending to shew the ana- 

 logy alluded to between these strata of sandstone in the 

 hilly part of Barbadoes, and those occurring in the Lowlands 

 of North Britain, that the former are associated with, or suc- 

 ceeded by, beds or strata of various clays, — ^by beds of silice- 

 ous matter composed almost entirely of the remains of infu- 

 soria, and by beds of chalk abounding in similar infusoria, 

 with seams or deposits of bituminous coal interspersed, — in 

 one instance mixed with anthracite, and with strata having 

 the character of volcanic ashes, — besides others. Thus ex- 

 hibiting, in a small space, an extraordinary variety, and this 

 the more remarkable from the contrast as to geological struc- 

 ture of by far the larger portion of Barbadoes, remarkable 

 for its uniformity. Its prevailing rock is an aggregate or 

 fragmentary one, consisting chiefly of shell and coral lime- 

 stone, and freestone, in many places abounding in species of 

 shells and corals identical with species existing at present in 

 the adjoining seas. 



It has been supposed by those who have hitherto written 

 on the geology of Barbadoes, that the shell and coral lime- 

 stone is lower in the series of rocks than sandstone, and the 

 other strata mentioned. But this is clearly a mistake. The 

 shell limestone may be seen resting on clay in some of the 

 sea-cliifs ; and some of the summits of the hills in the lesser 

 district are capped with freestone or shell limestone, in which, 

 in one instance, I have found the teeth of two different spe- 

 cies of shark. 



Paebadoes, 29«A May 1846. 



