Shortly after Davy’s return to England his sympathy was enlisted in a cause which enabled him to display all the attributes of his genius, and to achieve a triumph which, while greatly enhancing his popular reputation, added no little to his scientific fame. To show him how he might be useful, was at all times a certain method of securing his interest; for, like Lavoisier, he was even more the friend of humanity than of science, and to make science serviceable to humanity was, he considered, the highest object of his calling. During the early years of this century the country was repeatedly shocked by the occurrence of a succession of disastrous colliery explosions, especially in the north of England, attended by great destruction of life and property and widespread misery and destitution. The development of our iron-trade, the improvements in the steam-engine, and the more general application of machinery to industry had greatly stimulated the opening out of our coal-fields; and the working of coal was being extended with a rapidity that greatly aggravated the evils and dangers at all times inseparable from it. In the early days of coal-getting, when the pits were shallow and the workings comparatively near the shafts, fire-damp, although not unheard of, was little dreaded, and explosions were rare--so rare, indeed, that when they occurred they were thought worthy of mention in the _Philosophical Transactions_ of the Royal Society. As the pits became deeper, and the ways more extended, explosions became more frequent, and at times it was impossible to work the coal, owing to the accumulation of fire-damp and its liability to “fire” at the candles of the miners. In 1732 attempts were first made to ventilate the pits by “fire-lamps” or furnaces, and by mechanical means, so as to sweep out the “sulphur” by means of fresh air. Carlisle Spedding, a little later, invented the steel mill--a contrivance by which a disc of steel was caused to revolve against a piece of flint, so as to throw off a shower of sparks sufficiently luminous to enable the miner to carry on his business.