138 LIMESTONE FAMILY# burnt into quicklime, the marly varieties afford rather an indifferent mortar; but those mixed with sand a better mortar. Observations. 1* It passes into Sandstone, Limestone, and Marl. 2. Some naturalists, as Daubenton, Saussure, Spallan zani, and Gillet Lamont, conjecture, that Roestone is carbonate of lime, which has been granulated in the manner of gunpowder, by the action of water: the most plausible opinion is that which attributes the formation of this mineral to crystallization from a state of solu tion. 3. It is named Roestone, from its resemblance in form to the roe of a fish. Second Subspecies. Foliated Limestone. Blattriger Kalkstein, Werner. 1 his subspecies is divided into two kinds, viz. Foliated Granular Limestone, and Calcareous-Spar. First