The extraordinary expansion of the Scotch iron trade of late years has been mainly due to the discovery by David Mushet of the Black Band ironstone in 1801, and the invention of the Hot Blast by James Beaumont Neilson in 1828. David Mushet was born at Dalkeith, near Edinburgh, in 1772.[5] Like other members of his family he was brought up to metal-founding. At the age of nineteen he joined the staff of the Clyde Iron Works, near Glasgow, at a time when the Company had only two blast-furnaces at work. The office of accountant, which he held, precluded him from taking any part in the manufacturing operations of the concern. But being of a speculative and ingenious turn of mind, the remarkable conversions which iron underwent in the process of manufacture very shortly began to occupy his attention. The subject was much discussed by the young men about the works, and they frequently had occasion to refer to Foureroy's well-known book for the purpose of determining various questions of difference which arose among them in the course of their inquiries. The book was, however, in many respects indecisive and unsatisfactory; and, in 1793, when a reduction took place in the Company's staff, and David Mushet was left nearly the sole occupant of the office, he determined to study the subject for himself experimentally, and in the first place to acquire a thorough knowledge of assaying, as the true key to the whole art of iron-making. He first set up his crucible upon the bridge of the reverberatory furnace used for melting pig-iron, and filled it with a mixture carefully compounded according to the formula of the books; but, notwithstanding the shelter of a brick, placed before it to break the action of the flame, the crucible generally split in two, and not unfrequently melted and disappeared altogether. To obtain better results if possible, he next had recourse to the ordinary smith's fire, carrying on his experiments in the evenings after office-hours. He set his crucible upon the fire on a piece of fire brick, opposite the nozzle of the bellows; covering the whole with coke, and then exciting the flame by blowing. This mode of operating produced somewhat better results, but still neither the iron nor the cinder obtained resembled the pig or scoria of the blast-furnace, which it was his ambition to imitate. From the irregularity of the results, and the frequent failure of the crucibles, he came to the conclusion that either his furnace, or his mode of fluxing, was in fault, and he looked about him for a more convenient means of pursuing his experiments. A small square furnace had been erected in the works for the purpose of heating the rivets used for the repair of steam-engine boilers; the furnace had for its chimney a cast-iron pipe six or seven inches in diameter and nine feet long. After a few trials with it, he raised the heat to such an extent that the lower end of the pipe was melted off, without