The course of instruction consists of ten drills such as has been described, after which the men are called up twice a year, just to refresh their memories.
One side of the gallery is glazed, so that the instructor can watch his men at work without of necessity being inside himself, and there are emergency doors as well, which can be opened to let a man out should the ordeal be too much for him. The necessary "fumes" are generated in a stove and driven into the gallery by a fan. The stations are beautifully fitted up, with baths for the men to wash after their somewhat dirty experience in the gallery, and everything is done for their convenience and welfare.
The advantage of this systematic training of a great number of men is that there are men at each colliery who can be called upon when needed. The team of strangers, as has been remarked, partially failed at Courrières, largely because they were strangers, but when every colliery has a team ready, composed of its own men, then clearly there is the greatest chance of success. The central station of the district is the training-ground where the men go from all the collieries to get the experience and instruction, and where a reserve store of appliances is kept. In many cases, of course, the collieries have their own appliances, so that work can be begun at once, without having to wait for that from the rescue station, but the latter forms a reserve in case of need, and, being kept under the care of an expert, it is naturally always in the best possible working order.
To give an idea of the cost of these stations, it may be stated that the one at Porth, in the Rhondda Valley, cost, including equipment, £7000, while the one at Mansfield cost £3000. This first cost and the expense of maintenance is borne by the collieries of the district in proportion to the quantity of coal which they raise.
And now we can turn to the apparatus itself, without which the organisation already described would be of little value.
There are several makes of these, but a description of the particular apparatus used at the two stations mentioned will serve as an illustration. The purpose, of course, is to give the wearer an atmosphere of his own, which he can carry about with him, and which will render him quite independent of the ordinary atmosphere and quite indifferent to the poisonous nature of the gases around him. To this end his mouth and nostrils must be cut off from the outer world altogether. There are two ways of doing this. In the one there is used a helmet, or perhaps mask would be the better term. This fits right over the man's face, an air-tight joint being made between the helmet and his head by means of a rubber washer which can be inflated with air. The inflation is accomplished by squeezing a rubber ball on the right-hand side of the helmet. In the centre is a glass window through which he can see easily, and since this is apt to become clouded by the dampness of his breath there is a wiper inside, which can be turned by a knob on the outside, so that by simply turning his knob with his hand he can clean the window at any time that may be necessary. Two soft pads inside the helmet bear one on the man's forehead and the other on his chin, and these, working in conjunction with a strap which passes right round the back of his head, keep the thing firmly in position. In addition there is combined with the helmet a leather skull-cap which, being continued down behind, gives good protection to the head and neck.
The other form of apparatus consists of a mouth-piece and nose-clip. The mouth-piece, as its name implies, fits in the man's mouth, being supported and kept in position by a strap passing behind the back of his head. Combined with it is a little screw clip which closes his nostrils. The man also wears a leather skull-cap, from which straps depend to bear the weight of the mouth-piece and its attached tubes, so that the weight does not fall upon his mouth.
Either of these arrangements, it is clear, cuts him off from communication with the outer air, but that is only half the problem, for he must be given a substitute or he will be suffocated.
This part of the appliance he carries, knapsack fashion, upon his back. First there is a rectangular case, called the regenerator, with, below it, two small cylinders of compressed oxygen. A suitable arrangement of pipes connects these together, and to the helmet or mouth-piece as the case may be.
When the man exhales, as we all know, the air which he then discharges from his lungs is deficient in oxygen and instead contains carbonic acid gas. The latter must be got rid of and replaced by pure oxygen. The exhaled air is therefore led down a pipe to the regenerator, where it comes into contact with several trays of caustic soda, a chemical which has a great affinity for carbonic acid. The result is that the latter gas is extracted from the impure air, finding a more congenial home in the caustic soda. It is then necessary to restore the normal quantity of oxygen, and so, as the air passes on, it meets, in a little apparatus known as an injector, a spray of pure oxygen from the cylinders. Thus, after being purified and re-oxygenated, the air passes on through more pipes to the helmet or mouth-piece, to be breathed once more. The apparatus contains sufficient oxygen and caustic soda for this to go on for a space of two hours.