heaps, and to guard againt the spontaneous combustion, apt to ensue from the decomposition of small particles of pyrites, a dam is placed in the "bolt hole," and this portion cut off from all communication with the rest of the workings.
The second mode of getting, by what is called long work, need not be described at length, being very similar to that practised in Shropshire. Derbyshire, and other districts; it is, as elsewhere, variable according to the condition of the roof, &c., the road-ways being sometimes driven out through the "whole coal," which is then worked back towards the shafts, in other cases the roads being maintained through the "gob" or waste from which the coal has been removed, as the extraction proceeds from the shafts towards the limits of the field.
Very important, however, in an economical point of view, both to the lord of the soil, and to the lessee, as well as to the interest of humanity, is the success which has attended the efforts of certain coalowners to get the ten-yard coal on the principles of "long work," as exemplified in the pits of the Messrs. Foster, of Mr. Gibbons, and at Congreaves. We have seen that by the usual method, what with the ribs and pillars left untouched and the quantity of coal cut up into slack, a vast amount of useful fuel—of what in fact in a very few years must become of much higher value, is utterly lost to the nation.
It is not too much to assert, that from one-third to one-half of the coal is thus left useless, (some little only of the ribs and pillars being afterwards recoverable in a damaged copies} an amount of squandered natural advantages almost without a parallel.
By the common plan it is considered that 16,000 tons of coal obtained from an acre of ground represents a very fair produce, and no doubt's very much lower number is often obtained. At Messrs. Foster's, the coal is worked in two divisions, the upper half first, by long work, and then some months afterwards, when the "shut" or roof has fully subsided, the lower half is worked by the same method, and a total amount of from 26,000 to 31,000 tons of coal to the acre is procurable, and it need only be added to the conclusions suggested by a comparison of these numbers, that, under this newly applied system, there has been enjoyed a comparative immunity from those frequent and frightful accidents which have gained the workings of the Thick coal a most unenviable notoriety.
In conclusion, the ventilation of these works requires a short notice, from the fact, that although the coal is not highly charged with firedamp, very serious accidents have happened from explosions, and the every-day state of some of the pits cannot be regarded without dread. The establishment of a current of air is left much to accident; and the causes disposing the air to travel down one shaft and up the other are so easily disturbed by a change of wind, or other trivial cause, that a stagnation is frequently produced, or the pits are said to fight, and during the contest, if nothing more serious occurs, the colliers are obliged to "play" or absent themselves.
"Air-heads," of not more than 9 or 10 feet sectional area, are driven in the coal parallel with the gate-roads, and communicate with the "sides of work;" but unless, according to the suggestion of Ryan, they are driven in the upper part of the seam, there must frequently accumulate in those high working stalls a magazine of explosive gas ready to fire on the first opportunity, so easily afforded by a fall of coal, a change in the barometer, or the imprudence of a workman.
It need scarcely be observed how greatly the danger is augmented, when the "air heads" are not brought up simultaneously with the main workings, yet under the "butty" or "chartermaster" system, it is too
