The British fleet rounding Eddystone Lighthouse during the great storm of October, 1859.
The ingenious invention alluded to was succeeded by another and equally simple but philosophical arrangement, which Dr. Faraday presented to his brother, and it was duly patented. It consisted of an arrangement for ventilating gas burners, and it must be obvious that a necessity exists for such ventilation, because every cubic foot of coal gas when burnt produces a little more than a cubic foot of carbonic acid. A pound weight of ordinary coal gas contains about 3/10ths of its weight of hydrogen, which when burnt produces two pounds and 7/10ths of a pound of water. A pound of ordinary coal gas also contains about 7/10ths of its weight of charcoal, which produces when burnt rather more than two and a half pounds of carbonic acid gas—viz., 2.56. In order to burn this quantity of gas nineteen cubic feet and 3/10ths of a foot of atmospheric air, containing 4.26 cubic feet of oxygen, are required.
Fig. 374.
a b. Gas pipe and argand burner; the air enters, as usual, up the centre of the argand. c c. The first glass chimney open at the top. d d. The second glass chimney closed at the top, with a disc of double talc, and fitting over c c, and leaving a space between the two glasses, down which the air passes, and into the ventilating tube, e e. h h. The ground-glass globe closed at the top, and surrounding the whole.[I]
[I] Mr. Faraday, of Wardour-street, supplies this ventilating lamp.
It is not therefore surprising that as common coal gas is sometimes purified carelessly, and contains a minute trace of sulphuretted hydrogen, with some bisulphide of carbon vapour, that it should produce the most prejudicial effects in badly ventilated rooms, and especially in some of those perched up glass boxes in large places of business, where clerks are obliged to sit for many consecutive hours, lighted by gas, and breathing their own breath and the products of combustion from the gas light, thereby rendering themselves liable to diseases of the lungs, and also to very troublesome throat attacks, when leaving their close glass boxes, and passing into the cold night air. The dangerous product of the combustion of ordinary coal gas is sulphurous acid—viz., the same gas as that generated when a sulphur match is burnt; and if it will attack the bindings of books, and damage furniture, goods in shops, curtains, &c., in consequence of the large quantity of water with which it is accompanied, how much more is it not likely to injure the delicate organism of the breathing apparatus of the lungs? Dr. Faraday's lamp is therefore a great boon, but, like a great many other clever things, it must be adapted to the currents of air and draught from the room; and means must be taken to prevent the draught becoming too powerful in Faraday's lamp, or else the illuminating power is destroyed by the thorough combustion of the carbon of the coal gas, and the heat generated is so intense that the glasses soon crack, and of course become useless. The lamp will answer very well if (as has been already stated) the draught in the ventilating pipe is not too great.
The system already explained and illustrated is likewise carried out on a much larger scale in the ventilation of coal pits, where a shaft is usually sunk into the ground for the admission of air, which, after circulating through the intricate windings and mazes of the coal pit workings, escapes at last from another shaft, at the bottom of which is placed a powerful furnace, and this is kept burning night and day, so that the movement of the air is maintained in one direction—viz., from the outer air down the shaft called the downcast, thence to the galleries, where the coal hewers are working, to the second shaft, near which the furnace is placed, and up this latter the air travels; the shaft, pit, or funnel being very appropriately termed the upcast.
Should the furnace at the bottom of the upcast be neglected, the ventilation may be just balanced, or set slightly towards the downcast; under these circumstances the carbonic acid from the fire will begin to circulate in the galleries, and poison those who are not aware of its presence and take the proper means to escape. Such accidents, amongst the host of others that occur in a coal pit, have actually been recorded; and the firemen, whose duty it might be to attend to the proper burning of the furnace, have had to pay the penalty of death for their own carelessness in falling asleep and neglecting to maintain the ventilation of the mine in one direction. (Fig. 375.)