St. Austell measures 10,018 statute acres. The annual value of the Real Property, as £. _s._ _d._ returned to Parliament in 1815 4,628 0 0 The Poor Rate in 1831 2,890 6 0 Population, { in 1801, | in 1811, | in 1821, | in 1831, { 3788 | 3686 | 6175 | 8758. Increase on an hundred in thirty years, 131.2, or above 131 per cent. Present incumbent, the Rev. T. S. Smyth, presented in 1815 by the King. GEOLOGY, BY DR. BOASE. This parish, so important in an economical point of view, on account of its minal production, affords a vast fund of geological information. Its northern part is composed of granite; its southern part of various rocks belonging to the porphyritic group. Its granite on the eastern side is like that of Alternun, and contains layers which abound in porphyritic crystals of felspar. On the western side it comprises several kinds of this rock; some characterised by the proportions of shorl that enter into their composition; and others by containing talc instead of mica, and by the felspar being prone to an extensive decay, in which state it furnishes porcelain clay (or china clay) for the potteries. A more particular description of these kinds of granite will be given hereafter, in the accounts of St. Stephen’s, and of the adjacent parishes. Carclaze tin mine must not, however, be passed by, as it is one of the greatest curiosities in Cornwall. This mine is worked “open to the day” (according to the miners’ term), that is, like a quarry. It is of a considerable depth; and its superficies exceeds several acres in extent. It is excavated entirely in a white granite, somewhat similar to the disintegrating variety above alluded to; and when the sun shines, the reflection of light is so exceedingly dazzling as to be almost insupportable. The tin ore occurs here intermixed with shorl and quartz, in the form of short irregular veins, which traverse the granite in every direction, and so abundant, that the whole rock requires to be pounded and washed to complete an entire separation of the ore.