Recent calcareous Breccia. 33 



warmer latitudes. Dr. Paris has given an account of a mo- 

 dern formation of sand-stone on the northern coast of Corn- 

 wall* ; where a large surface is covered with a calcareous sand, 

 that becomes agglutinated into a stone, which he considers as 

 analogous to the rocks of Guadaloupe ; and of which the spe- 

 cimens that I have seen, resemble those presented by Captain 

 Beaufort to the Geological Society, from the shore at Rhodes. 

 — Dr. Paris ascribes this concretion, not to the agency of the 

 sea, nor to an excess of carbonic acid, but to the solution of 

 carbonate of lime itself in water, and subsequent percolation 

 through calcareous sand ; the great hardness of the stone arising 

 from the very sparing solubility of this carbonate, and the 

 consequently very gradual formation of the deposit. — Dr. Mac 

 Culloch describes calcareous concretions, found in banks of 

 sand in Perthshire, which " present a great variety of stalactitic 

 forms, generally more or less complicated, and often exceed- 

 ingly intricate and strange f," and which appear to be analogous 

 to those of King George's Sound and Sweer's Island : — And 

 he mentions, as not unfrequently occurring in sand, in different 

 parts of England (the sand above the fossil bones of Norfolk 

 is given as an example), long cylinders or tubes, composed of 

 sand agglutinated by carbonate of lime, or ' calcareous sta- 

 lactites entangling sand,' which, like the concretions of Ma- 

 deira, and those taken for corals at Bald-Head, tr have been 

 ranked improperly, with organic remains." 



The stone which forms the fragments in the breccia of New 

 Holland, is very nearly the same with that of the cement by 

 which they are united ; — the difference consisting only in the 

 greater proportion of sand which the fragments contain : — and 

 it would seem, that after the consolidation of the former, and 

 while the deposition of similar calcareous matter was still in 

 progress, the portions first consolidated must have been shat- 

 tered by considerable violence. But, where no such fragments 

 exist, the unequal diffusion of components at first uniformly 

 mixed, — and even the formation of nodules differing in pro- 

 portions from the paste which surrounds them, may perhaps 

 admit of explanation, by some process analogous to what takes 

 place in the preparation of the compound of which the ordi- 

 nary earthenware is manufactured ; — where, though the ingre- 

 dients are divided by mechanical attrition only, a sort of che- 

 mical action produces, under certain circumstances, a new 

 arrangement of the parts %. And this explanation may, pro- 



* Trans, of the Geol. Soc. of Cornwall, vol. i. p. 1, &c. 



t " On an arenaceo-calcareous substance," &c. — Quarterly Journal 

 (Royal Institution), Oct. 1823, vol. xvi. p. 79-83. 



X The clay and pulverized flints are combined for the use of the potter, 

 Vol. 68. No. 339. July 1826. E by 



