augmented by an inequality in the length of the two ends of the lever. It must be considered too, that one-third part only of the coals which the old engine would have required, is used for the same portion of work.” The expense of erecting the first steam engine in the Polgooth Mine, amounted to nearly £20,000; and the quantity of coals consumed by it, in the short space of 24 hours, is stated to amount to 144 bushels. According to Borlase, the main vein of ore in this mine, was about six feet thick, running from east to west, and dipping to the north, at the rate of about six feet in a fathom; towards the east it divides into two branches, and there is another that cuts the former nearly at a right angle, and consequently runs north and south, but dipping to the east. The _ore_ is disseminated in general through a matrix of _Caple_,[49] accompanied with a _yellow cupreous pyrites_, and sometimes a _ferrugineous ochre_; it is of the vitreous kind, but rarely found in crystals, the colour for the most part being of a greyish brown. _Crennis Copper Mine_, which is situated about two miles east of St. Austell, is highly deserving of notice: here also steam engines have been introduced with the most beneficial effects; but although the ore found in this mine is extremely rich, it was not discovered till within the last few years, but is stated in some instances to have yielded a clear profit to its proprietors of £84,000 in one year. The several _Tin Stream Works_ also in the neighbourhood of St. Austell, are particularly deserving of notice; the one on the left of the road near Pentuan, has proved a considerable benefit to the adventurers concerned in it. In Luxilian parish, through which the road leading from St. Austell to Bodmin has been formed, there are several works of a similar nature; but owing to the number of excavations which have been made for the discovery of ore, it is desirable that strangers should avoid travelling in this direction after dusk. The celebrated _Wood Tin_, as it is called, is mostly found in the Stream Works, and which although extremely valuable, appears far from prepossessing in the minds of those persons who are unacquainted with mineralogy. Small particles of gold are frequently found in the Stream Works, but they are mostly incorporated with tin crystals in streaks.