Student's textbook of hygiene / [William James Wilson].

  • Wilson, William James.
Date:
[1915]
Catalogue details

Licence: Public Domain Mark

Credit: Student's textbook of hygiene / [William James Wilson]. Source: Wellcome Collection.

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    mitigate the smoke nuisance commonly met with in towns. Disadvantages are—(1) That they are apt to render the air so dry as to be irritating to the throat, and in certain individuals to cause headache. ‘The placing of a saucer of water near the fireplace assists in preserving the humidity of the air. (2) That they are rather more expensive than coal, but where water-gas is used this is not the case. In Belfast, where a mixture of coal-gas and carburetted water- gas is supplied, the cost of 1,000 cubic feet is two shillings and threepence. <A gas-fire burns on an average 20 cubic feet per hour. Before dealing with other systems of heating it is necessary to consider the three ways by which heat travels—by radiation, conduction, and convection. The heat that emanates from the front of an open fire is mainly radiant—+.e., it passes out in straight lmes without heating the air through which it passes. Dull black surfaces possess higher emissive powers for radiant heat than those that are bright, and also are better absorbers. The intensity of radiant heat is inversely as the square of the distance of the heated object from the source of heat. By conduction the fire- place and its immediate surroundings obtain heat from the fire, the heat being transmitted from particle to particle of these objects. Similarly, in hot-water pipes the pipes gain heat by conduction from the hot water circulating in them. By con- vection is meant the transmission of heat by actual motion of the parts of a heated fluid. The heat experienced when a hand is held over the fire or over any hot object is mainly conveyed by particles of air which, being heated through contact with the hot object, become lighter, and ascend. Stoves give out far more heat into the room than open fires, and are therefore more economical. There are two types— (1) The closed stove which in the process of combustion makes use of the air of the room; (2) ventilating stoves, which are provided with an air-duct under the floor for the admission of cold fresh air into a chamber surrounding the fire, in which the air is heated and then ascends into the room. A good example of such a stove is the Musgrave. The surfaces of stoves exposed to the fire should be lined with