Magic Lantern slide circa 1900 hand coloured. created in 1887. A tour of North Wales. 18 Penrhyn Slate Quarries.??”These are the property of Lord Penrhyn, and an inspection will well repay the tourist. They are of very large extent, being nearly a mile across from one side to the other, and every modern mechanical arrangement is brought to bear upon the working of them. Everything in connection, from the busy toilers to the tremendous ranges of galleries formed one above another, combine to produce astonish-ment at the enterprise which has so usefully employed these mountain wastes. The usual blasts take place every hour, when the noise rolls along the mountain sides like peals of thunder. An immense pillar of rock, computed to weigh 125,000 tons, that had been left near the middle of the Quarry was blown up in April, 1895, by two blasts of powder amounting to seven tons. There are 3,000 persons engaged in these Quarries, and an average of 200 tons of slates is daily conveyed to the port at Bangor.