There were some curious Celtic lines which described the age of animals compared with that of man: 

  Thrice the age of a dog is that of a horse;
  Thrice the age of a horse is that of a man;
  Thrice the age of a man is that of a deer;
  Thrice the age of a deer is that of an eagle.

The ages of man were divided into three by Lucretius as: 

  (1) “The Stone Age,” when celts or implements of stone were employed.
  (2) “The Bronze Age,” when implements were made of copper and brass.
  (3) “The Iron Age,” when implements were made of iron, as in the present
          day.

This being the order of antiquity and materials employed in making the implements, it was therefore safe to conclude that the mining of tin must have dated back as far as the Bronze Age, for there could have been no bronze made without tin, since bronze is produced by the mixing of copper and tin.

Appliances for crushing and smelting the ore were already in existence in very early times, as well as blowing-houses and moulds in which to run the molten metal.  The ingots of tin were in the form of an astragal, and an ancient ingot of large size dredged up in Falmouth Harbour, weighing 150 lbs., resembled the letter H in form.  This was the most convenient shape for carriage, either in a boat or slung across the back of a horse, and horses were employed in that way to convey the tin along the steep and narrow roads from the mines to the sea-coast.

The Romans made use of the Cornish mines, for an ingot of tin bearing a Roman stamp and inscription was preserved in the Truro Museum, and Roman coins had been found in the mines.

With St. Austell’s Bay to our left, we soon came in sight of the town of St. Austell, behind which were the Hensbarrow Downs, rising over 1,000 feet above sea-level.  From the beacon on the top the whole of Cornwall can be seen on a clear day, bounded by the Bristol Channel on one side and the English Channel on the other; on the lower reaches, and quite near St. Austell, were the great tin mines of Carclaze, some of the largest and most ancient in Cornwall.

Another great industry was also being carried on, as in the year 1768 W. Cookworthy, a Plymouth Quaker, had discovered an enormous bed of white clay, which had since been so extensively excavated that the workings now resembled the crater of an extinct volcano.  This clay, of the finest quality, was named China clay, because it was exactly similar to that used in China, where porcelain was made many centuries before it was made in England, the process of its manufacture being kept a profound secret by the Chinese, whose country was closed to Europeans.