Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/456

 Renfrewshire. The strata of the four places vary indeed in thickness, but their position and alternation may be considered the same. A sketch of the Campsie strata is subjoined, as descriptive of the whole.

The coal has been extensively excavated for a long series of years, from mines of which the temperature is seldom under 60° Fahr. frequently as high as 80°, in places excluded from any direct current of air. The circulation of this warm air has ripened the hard slate into various qualities, and these contain proportions of alum and copperas, which vary according to the time of their exposure, the recent slates abounding in copperas, those longer exposed, in albuminous matter.

A notice was communicated by Leonard Homer, Esq. respecting the rocks of the Isle of Tino, in the Archipelago.

The highest part of Tino is one long ridge of limestone, which affords excellent marble, that is sent for grave-stones to Smyrna and Constantinople. In the garden of an Italian convent there is a beautiful vein of asbestos running through serpentine, which passes into a kind of verde antique. Ut is stratified and dips westward