The wacke has a greenish gray colour, which is pretty uniform. The fracture is nearly even and earthy, it is soft, yielding readily to the nail, and has a feebly shining streak. A slight stroke with the hammer causes the mass to separate in fragments of various size, the surfaces of which are often smooth and shining, each bed being composed of large distinct concretions, having a tendency to the prismatic form. This wacke fuses with difficulty before Brooke's blow-pipe. Specific gravity not determined, as it falls to pieces on being moistened. The sandstone is for the most part gray, in some parts spotted red and brown, forming, as the section represents, the last stratum seen; the beds of sandstone are but a few inches in thickness, and the last (17) becomes less than an inch; it is probable, however, from the relative situation, from the dip and direction, that these strata are a continuation of others seen on the other side of the hill, where they are of sufficient thickness to have been quarried for the purposes of architecture. The _beds_ of all rocks we know vary greatly in different parts, and it is not unusual for them to be some feet at one extremity, gradually decreasing till less than an inch in thickness at the other, or they may even be lost entirely, and gradually regain their former size; and it is not improbable that these beds of sandstone will be found to continue on towards the adjoining hills of Salisbury Craig and Arthur's Seat, passing under the greenstone and trap tuff. The bituminous shale presents the usual characters; intermixed with it are numerous nodules of the common clay ironstone, the colour of which is a yellowish brown, these also frequently present characters common to the three substances, and throughout the beds, the passage from the one to the other is distinct. Whatever may be the opinions in regard to the origin of bituminous shale, there can be but one in regard to that of sandstone; and this has lately received no feeble support from the account given us by Dr. Paris, of a formation of this rock on the coast of Cornwall, where, says he, "we actually detect nature at work, and she does not refuse admittance into her manufactory, nor conceal, with her accustomed reserve, the details of the operations in which she is engaged." From the appearances which have been thus briefly noticed, no impartial geologist, we should imagine, would infer the _volcanic_ origin of any portion of this formation; and if the aqueous origin of sandstone can be established, that of the wacke must be the same. * * * * * From its intimate connexion with the preceding subject, Dr. Webster subjoins the following: _Extract from a Paper on a recent formation of Sandstone, occurring in various parts of the Northern coast of Cornwall_; by JOHN AYSTON PARIS, M.D. F.L.S., &c. &c. Published in the Transactions of the Geological Society of Cornwall, 1818.