dog, and the candles show it. They seem to be heavy sulphurous airs, not fit to breathe, and I have heard some say that they would sometimes lie in the midst of a shaft and the bottom be clear. The flame of a candle will not kindle them so soon as the snuff, but they have been kindled by the striking fire with a tool. The blast is mighty violent, but men have been saved by lying flat on their bellies."

At the same period fire-damp had become formidable in the collieries near Mendip Hills, in Somersetshire. An account written in 1681 states that "many men of late years have been there killed, many others maimed and burnt; some have been blown up at the works' mouth, the turn-beam which hangs over the shaft has been thrown off its frame by the force of it."

In the collieries of Scotland fire-damp was more rare, but was not unknown. The trouble which it occasioned was assigned as one of the causes for abandoning a colliery on the Frith of Forth previous to 1672.

During the seventeenth century many under-ground fires occurred, particularly in Staffordshire, where they were so common as to excite comparatively little anxiety. These fires were sometimes attributed to the malice or carelessness of the colliers; but the liability of some coals to ignite spontaneously was now well known. Fires from this cause had occurred above-ground also, both

1 Another writer of this period mentions that fire-damp had been kindled in some places "by the motion of the sled in which they draw their coals."

on the staiths at Newcastle and on the wharves at London. Coals containing pyrites (termed metal coals) were peculiarly liable to ignition in this way. Dr. Power mentions an instance which occurred at Ealand, in Yorkshire, where a person had collected many cartloads of this pyrites for some private purpose of his own. The roof of the place where they were stored being faulty and admitting rain-water to fall copiously in among them, they began to smoke and then took fire and burnt like red-hot coals, "so that the town was in an uproar about the quenching of them."

CHAPTER VIII.

INADEQUACY OF THE WATER-RAISING MACHINERY.— INVENTION OF THE STEAM-ENGINE.

“It is a giant with one idea.”

-COLERIDGE.

IN the beginning of the eighteenth century the common depth of the mine shafts in the North of England was from twenty to thirty fathoms, but a few had attained to depths of fifty or sixty fathoms. The deeper shafts were already entering the drier region below the zone of watery strata (which usually extends to a depth varying from fifty to a hundred fathoms from the surface), where difficulties with water begin to grow less, while difficulties with fire-damp increase in magnitude. In these deeper shafts the process of tubbing out the water by means of water-tight timber frames could already be practised with considerable success; but in the great majority of cases water continued to harass

or even altogether baffle the miners: sometimes preventing them from reaching the coal in spite of all their arts, or entailing a ruinous expense in carrying on the collieries, so much so as in some instances to occasion their abandonment.

The chain of buckets was soon found to be inadequate to meet the ever-increasing wants of the miners. Without water-power to drive these engines they were of little use; and even where this was available, this kind of machine was open to many serious objections. The wear and tear was excessive; between vibration of the chains and leakage, half of the contents of the buckets was spilled before they arrived at the top; water was constantly pouring down the pit like a deluge; and when a bolt broke the whole set of chains and buckets fell to the bottom with a most tremendous crash, and every bucket was splintered into a thousand pieces.

Hence a widely-felt want existed for a suitable machine to raise the water from the mines. In the year 1708 a plan was projected in Scotland for draining collieries by means of windmills and pumps, but so backward was the state of engineering art in the country that no person was known competent to put the scheme into execution except one John Young, a millwright of Montrose, who had been sent to Holland at the expense of the town to inspect the machinery there. It was suggested

that if the services of this person could not be obtained advice on the matter should be sought from the Mechanical Priest of Lancashire. Windmills were erected at several collieries, but though they were powerful their action was found to be too intermittent; the mines being drowned and all the workmen thrown idle during long periods of calm weather.

Pumps, however, being free from many of the defects of the chains of buckets, began to be substituted for them. We find the Earl of Mar, proprietor of Alloa Collieries in Clackmannanshire, having his water-engines altered in this way in 1710, on the recommendation of Mr. George Sorocould, an eminent engineer from Derby, whom he had called in to report on this and other matters connected with the machinery at his collieries. The alteration was found to effect a great improvement.

But the points where water-power could be obtained to drain the mines were comparatively few, and windmills, as we have seen, could not be relied upon; hence in far the most cases horse-power had to be employed, the water being drawn in barrels by means of a gin of the same description as that employed in drawing the coals. This power was capable of universal application, but it was of a limited and expensive character. In some instances as many as fifty horses were employed in raising