Obs. All the preceding preparations are intended for chilblains before they break. The liniments of ammonia, camphor, opium, soap,
and turpentine, as well as the compound camphor liniment of the British Pharmacopœia, are also excellent preparations for the same purposes.
CHIL′DREN (Care of). See Infancy.
Children (Diseases of). See the respective heads, and Diseases.
CHIL′LIES. See Capsicum, Peppers.
CHIM′NEYS were not introduced into England until the reign of Queen Elizabeth, and for a considerable period the principles of their construction were ill-understood. When the air inside and outside a chimney is at the same temperature, an equilibrium exists; there is no draught in the chimney, because the downward tendency of that within is counteracted by the upward pressure of that without. Let a fire be kindled in the grate; hot air is evolved, the chimney is heated, the air it contains suffers expansion, and a portion is expelled. The chimney now contains a smaller weight of air than it did before; the external and internal columns no longer equibalance each other, the warmer and lighter air is forced upwards from below, and its place is occupied by cold, and consequently heavier air. If the fire continues to burn, and the chimney retains its temperature, the second portion of air is disposed of like the first, and the ascending current continues, so long as the sides of the chimney are hotter than the surrounding air. Should the reverse happen to be the case, as sometimes occurs from sudden atmospheric changes, the column of air within the chimney rapidly contracts in volume, the deficiency is filled up from without, the column of air becomes heavier than one of a corresponding height on the outside of it, or in the apartment, and, obeying the common laws of gravitation, it falls out of the throat of the chimney or fire-place just as a heavy body sinks in water, and has its place occupied by air from above. In this way a descending current, of more or less intensity and duration, is established, and, if there is a fire in the grate, the chimney “smokes,” or, if the grate is empty, perhaps the smoke from neighbouring chimneys finds its way into our apartments. By the judicious arrangement of the fire-place, and the throat and flue of a chimney, an upward current may be constantly ensured so long as there is a fire in the grate, or the air of the apartment is warmer than the external atmosphere.
Count Rumford was the first who scientifically investigated the construction of chimneys. He showed that more heat is obtained from the fire by reflection when the coverings are placed in an oblique position. He also directed that the fire itself should be kept as near to the hearth as possible, and that the throat of the chimney should be constructed much narrower than was then the practice, in order to prevent the escape of so much heated air as happened with wide throats. By contracting the open part of the fire-place immediately over the fire, as by lessening the width of the hobs, or by bringing the throat of the chimney closer to the fire, and by contracting the throat of the chimney itself, within certain limits, any desired amount of draught may be obtained. When the space above the fuel is too small, the throat too near the burning fuel, or the throat itself too contracted, the draught of a common chimney is often too strong, and much fuel and heat is wasted. When the reverse is the case, the draught is commonly too languid, the fire draws badly, a portion of the smoke escapes into the room, and all the usual annoyances of a smoky chimney are suffered. By a proper attention to these conditions a common fire-place may be adapted for the combustion of bituminous or easy burning coal, or of anthracite, and varieties of coal that require a considerable draught. It may even be converted into a wind furnace; whilst the inconvenience of smoky chimneys may be always avoided, and, when existing, easily cured. This is presuming, however, that a sufficient supply of air exists in front of the fire-place (i.e. in the apartment), not only for the combustion of the fuel, but also for the upward current of the chimney. Many chimneys smoke simply from the apartment being so ill-ventilated that the supply here alluded to is not provided. It may be further stated, as a rule, that the greater the length of a chimney the stronger will be the draught. Hence, the chimneys of the upper rooms of a house often smoke, whilst the fires in the rooms beneath them burn pleasantly and vigorously. Such cases are commonly relieved by a chimney-pot or cowl, of which numerous varieties are now before the public. The more crooked or tortuous the course of a chimney the less likely is it to be affected by eddies and gusts of wind from neighbouring buildings or hills. See Fire, Grate, Smoke Prevention, Stove.
CHI′NA. In the purchase of china, glass, and earthenware, care should be taken to select those patterns which in case of breakage can be the most readily matched. Peculiar or rare patterns should be avoided, for if any such be broken, it will generally be found very difficult and expensive, and frequently impossible, to replace them.
China, glass, and earthenware, when very dirty, are best cleaned with finely powdered fuller’s earth and warm water, followed by rinsing in clean water. A little clean soft soap may be added to the water instead of fuller’s earth. See Packing, Porcelain.
CHIN′OIDINE. See Quinoidine.