Schistose Talc

To the remarkable Sandstones figured at tab. 413, I now add a curious and strange Chlorite Slate or Schist as, which is equally remarkable, or perhaps more so, as the concentric rings and strife apparently depend upon some more unaccountable action, which, from the appearance of the specimens, spread largely, and continue making their formal progress to an uncommon extent. The two upper figures are from the well-known Slate quarry at Ingleborough in Yorkshire, by favour of the friendly Mr. Dauby. They do not ill represent the kind of markings and knots of a deal board where the harder and turpentine part is most distinct in form. The markings on the other figure curiously represent the old-fashioned marble paper.

The lowest delicate specimen is of a looser and more sandy texture. This and some odd varieties were found in digging the foundation of the Infirmary at Bristol. It is worthy of observation, that these figurative lines are generally placed so as to be contrary to the lamellar structure of the Slate, and therefore are not interrupted by the divisions or lamellar fracture. Such appearances may be formed in some more or less perfectly formed Sandstones, with a similar laminated fracture, and especially when near or accompanying the common Slate.