| Population,— | |||
| in 1801, 990 | in 1811, 1248 | in 1821, 1558 | in 1831, 1728 |
giving an increase of 74½ per cent. in 30 years.
THE GEOLOGY, BY DR. BOASE.
This parish is similarly constituted to the adjacent parishes of St. Erth and Gwinear, being all situated on a line running north-east and south-west, between the large masses of granite of the Land’s End and of Cambrea.
St. Michael’s Mount, adjoining the shore of this parish, is an object of great attention to the geologist as well as to the tourist. It is composed almost entirely of granite, having only two small patches of slate, one on the western and the other on the eastern side; at these two places, and more particularly at the latter, the junction of the granite and of the slate may be seen, the slate being intersected with numerous granite veins. The granite of the Mount is not so large-grained as that of the Land’s End; but the structure of the rock is no where better displayed than at
this place on the southern side; where the whole mass is distinctly divided into large quadrangular blocks, and is traversed in a direction parallel to the divisions, by quartz veins, which contain crystals of mica, of apatite, and of topaz, and also the ores of tin, copper, and wolfram, the latter of which is the most abundant.
One most important geological fact is here beautifully exhibited. That the mineral composition of granite is altered in the vicinity of quartz veins, whether they are metalliferous or otherwise; approaching these veins the granite becomes more and more siliceous, until at length it gradually passes into the quartz, which forms the body (or matrix as it is called) of the veins. A fact difficult to reconcile with the generally received opinion, which assumes all veins to have been originally fissures, subsequently filled up from above or beneath.
[6] William of Worcester.