Page:The parochial history of Cornwall.djvu/269

Rh {| giving somewhat more than an increase of 53½ per cent. in thirty years.
 * Population, |||in 1801, 1816 |||in 1811, 2070 |||in 1821, 2493 |||in 1831, 2790;
 * }
 * }

Parish Feast, the nearest Sunday to the 17th of November.

A small portion of the southern part of this parish, adjoining to St. Dennis, rests on granite, the surface of which abounds in projecting masses of shorl rock. Leaving this granite district about the Indian Queens, on the Great Truro Road, a tin mine, called the Fat Work, presents itself, and displays some interesting phenomena. The basis of the rock is a compact felspar, sometimes almost colourless, at other times dark blue and glossy; but more commonly both these kinds are blended together in stripes or spots like agates. This rock next the lode is much decomposed, the blue parts being changed into a light pink; which shows that the colouring mineral is not hornblend. It is probably shorl, a substance abounding in the quartz veins by which the rock is traversed. The lode of this mine is very curious. It consists of a large massive rock, fifteen fathoms in width, throughout which shorl, and irregular veins of tin ore, are dispersed. The matrix consists of a dark-coloured basis, interspersed by innumerable angular and fragment-like portions of rock.

Near the Indian Queens a manganese mine was formerly worked, and the adjacent moors abound in stream works.

A fine blue fissile slate occurs around the town of St. Colomb, and continues for some distance northwards. Near Trewan it is found to contain beds of compact rocks (not unlike those of the Mount Bay), which inclose veins of actynolite. Still proceeding northward, quartz so much prevails, as to occasion sterility in the