In its natural state the flint presents itself in the shape of nearly round lumps, which are brittle, but nevertheless very hard, and which, like glass, can be split in any direction by a blow, so as to furnish scales with sharp edges. In consequence of this circumstance, all that would be requisite in order to produce sharp objects is to cleave off flakes in the shape of a knife or poniard, by striking a flint, held in the left hand, with another and harder flint or hammer. Instead of holding in the left hand the flint which was to be wrought, it might also be placed on a rest and, being held fast with the left hand, suitable blows might be applied to the stone. We must not, however, omit to mention, that to enable the flint to be cut up into sharp splinters and to be broken in any desired direction, it is necessary for it to have been very recently extracted from the bosom of the earth; it must possess the humidity which is peculiar to it, with which it is impregnated when in its natural bed. If pieces of flint are exposed to the open air they cannot afterwards be readily broken with any degree of regularity; they then afford nothing but shapeless and irregular chips, of an entirely different character from that which would be required in fashioning them. This moisture was well known to the workmen who used to manufacture the gun-flints, and was called the _quarry damp_. The necessity that the flint should be wrought when newly extracted from the earth, and that the stones should only be dug just in proportion as they were wanted, brought about as a proximate result the creation and working of mines and quarries, which are thus almost as ancient as humanity itself. Being unable to make use of flints which had been dried in the air, and consequently rendered unfit for being wrought, the workmen were compelled to make excavations, and to construct galleries, either covered or exposed to the open air, to employ wooden battening, shores, supports; in short, to put in use the whole plant which is required for working a stone-quarry. As, in order not to endanger the lives of the labourers, it was found necessary to prevent any downfalls, they were induced to follow out a certain methodical system in their excavations, by giving a sufficient thickness to the roofs of the galleries, by sinking shafts, by building breast-walls, and by adopting the best plan for getting out the useless _detritus_. When, as was often the case, water came in so as to hinder the miners, it was necessary to get rid of it in order that the workmen should not be drowned. It was also sometimes requisite that the galleries and the whole system of underground ways should be supplied with air. Thus their labour in fashioning the flint must have led our ancestors to create the art of working quarries and mines.