On an arenaceo-calcareous substance, etc.

Quarterly Journal Royal Institution October 1823 volume 16 page 79 to 83.) 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 shattered 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 proportions 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 ordinary earthenware is manufactured; where, though the ingredients are divided by mechanical attrition only, a sort of chemical action produces, under certain circumstances, a new arrangement of the parts.* And this explanation may, probably, be extended to those nodular concretions, generally considered as contemporaneous with the paste in which they are enveloped, the distinction of which, from conglomerates of mechanical origin, forms, in many cases, a difficulty in geology.

What the degree may be, of subdivision required to dispose the particles to act thus upon each other, or of fluidity to admit of their action, remains still to be determined.
(*Footnote.

The clay and pulverized flints are combined for the use of the potter, by being first separately diffused in water to the consistence of thick cream, and when mixed in due proportion are reduced to a proper consistence by evaporation.