20,000,000 had been attained in the engine at Herland, that shrewd philosopher pronounced the work perfect, and stated that further improvement could not be expected. Left, however, to themselves, by the expiration of Watt's patents, and the withdrawal of his agents from the county, the Cornishmen after a few years organized, in 1811, a system of monthly reporting the engines, with their conditions of work, and the duty accomplished. Within a space of some twenty-five years marvellous results were produced by the emulation thus aroused among mine-captains in the arrangement of their pit-work, and among engineers in the devising of improvements in boiler and engines.

As some of the modifications to be specially cited are, (1) Trevithick's tubular boiler for generating high pressure steam, where the fire is applied at the large end of the tube, and the heated air made to pass through it, then beneath the boiler or outer tube, and afterwards along its sides; 2ndly, the expansion in the cylinder of the high-pressure steam by closing the inlet valve at , 3rd, 4th, or even th of the stroke, whereby from 41 to 60 per cent. of the fuel is saved; and 3rdly, the addition of a steam jacket or outer case to the cylinder, so protected by a brick wall, casing of sawdust, or other clothing, that the internal space is occupied by steam of a temperature but little below that in the cylinder.

From an average duty of 17,000,000 performed in Watt's time, the Reports published by Lean show an amount of 28,000,000 attained in 1823, and of no less than 60,000,000 in 1843, whilst the best engine then tested had actually given an average duty of above 96,000,000! The most remarkable case on record is that of Austen's engine of 80 inches diameter, erected by

Mr. William West, at Fowey Consols Mines, and which, on being reported in 1834 to give a duty of nearly 98,000,000, was the occasion of a searching investigation and of a practical experiment, conducted by other engineers and mine agents, formed into a committee.* The shaft was at that time 131 fathoms below the efflux point of the water, the lifts of 15 inches diameter for the three upper, and 10 inches for the two lower ones; the length of stroke 9 feet 3 inches, the pressure at the boiler 36 to 45 lbs. per square inch. The astonishing result was, a declared duty for the twenty-four hours of experiment, of 125,000,000 !

On taking the average duty all through the year at 91,672,210, we find that, as burnt in this way, one ton of coal will do the work of five tons in Watt's engines, and will raise for 100 fathoms in height as much as 367,000 gallons, or 1,638 tons of water; whence, taking coal in Cornwall at an average price of 15s. per ton, the fuel costs one farthing to raise 21 tons of water 100 fathoms. The coal consumed for the long single-tube boilers of the Cornish engine is Welsh, shipped from Llanelly and Swansea, mostly small, and weighing 94 lbs. to the bushel. The combustion is very slow, but so perfectly effected, that a few years ago scarcely a puff of smoke was to be seen between one end of the county and the other. Of late it is true that a black pennant is occasionally visible, and the blame is laid upon inferior coals. But, at the same time, it is observable, that a very small number of the engines

Similar experiments by a committee had shown, in December, 1827, that Woolf's engine, at the Consolidated Mines, gave 63,663,473 lbs. duty, and Grose's engine, at Wheal Towan, St. Agnes, in 1828 87,209,662 lbs.

are reported, and the average duty has deteriorated; and thus, whilst the shareholders grudge the guinea or two per month for engineer's or reporter's fee, they pay heavily in increased coal-bills.

Among the most experienced of our mine-engineers in Cornwall, may be mentioned Captain Grose, Messrs. Harvey and Co., of Hayle, Messrs. Hocking and Loam, and Mr. West, of St. Blazey. Engines on a similar construction have been built elsewhere, at Messrs. Fairbairn's and many other works, both at home and abroad. But there has been wanting a fair system of reporting the results obtained; and when we see the great strides which accompanied the recording and publishing of the details in our western counties, it appears most desirable that such reports should become more general, and should include coal districts, in which we too often have to witness miserable exhibitions of neglect, extravagant use of fuel, and great wear and tear of materials. To compare a bad case with a good one, I have watched a large pumping engine in the north, which raises water from 105 fathoms deep, in 12-inch lifts, at 74 strokes per minute, with a consumption of 20 to 25 tons of slack per day. A similar amount of work is done by an average Cornish engine with from 2 to 21 tons. The coal is, doubtless, in the former instance inferior, but the result shows that there are engines in the country consuming upwards of ten times the quantity of coal that is needed for the work accomplished!

At the beginning of the century, it was proposed by Bull, to omit the heavy beam, or bob, which constitutes a great part of the dead weight of the common pumping engine, to place the cylinder over the shaft, and connect the piston-rod, working through the bottom, directly

with the main rod of the pumps. The Bull-engines have been erected at many mines, but have failed to compete with the others. Of late years, several have been established at collieries in this country and abroad, but their effective performance is doubtful. Another modification is just now in fashion in the coal districts, although condemned, after long experience, in Cornwall, viz., that of inverting the cylinder and placing the beam below it. But the piston-rod can hardly upon this system be so well lubricated, nor the stuffing-box kept in equally good condition, and the asserted saving in the building of the engine-house seems at best to be a very questionable piece of economy.

The fearful loss of life occasioned by the fracture of the main beam at the Hartley Colliery, has been the cause of further attention paid to that part of the engine; and several methods of substituting wrought for cast iron have been applied. At Clay Cross, the beam of the new 84-inch engine is formed of two slabs of rolled iron 36 feet long, 7 feet deep in the centre, and 2 inches thick, the two braced by strong cast-iron distancepieces bolted between them, the whole beam weighing 32 tons. At North Seaton and Cambois, near Newcastle, and at East Caradon, and other mines in the west, beams have been variously built of boiler plate and angle-iron; but it yet remains to be seen, what mode of construction will best ensure that rigidity which cast iron, with all its faults, must be acknowledged in a high degree to possess.

CHAPTER XVI.

LIGHTING OF THE WORKINGS.

THE collier, in descending to his work, seldom needs to carry a light through the shaft. A few seconds, when the machinery is good, or minutes where it lacks power, are sufficient to land him at the bottom, either in the dense gloom of a pit eye, rendered barely visible by a candle, or a safety-lamp, or, according to the circumstances of the colliery, in a busy scene of activity, well lighted by oil lamps or even by gas. Here, or at some station not far in-bye, he will light up, and, after a little delay, in order to accustom the eye to the darkness, proceed on his inward way.

The lamps of the well-known classical form, of which the Romans have left us numerous examples in bronze and terra cotta, survive in many of our modern underground workings, but especially in the metal mines of the Continent. In the collieries more generally their form has been changed to one with a globular, cylindrical, or conical oil-holder, and with a much smaller wick than would be used in the Roman lamp. The Scotch and some of the Saxons employ a little metal oil-lamp, with a hook on one side, by which it may be attached to their cap when travelling in low places on hands and feet, or when climbing ladders. In pits about Mons, in Belgium, an oblate form is preferred, resting upon a strong iron spike, by which it may be fixed into wood, or into the coal itself, at the required point of work. Lamps of this kind may be constructed to give a very tolerable light with vegetable oils, at the