[The dwelling-house in relation to health : a lecture] / by Henry Simpson.
- Henry Simpson
- Date:
- [between 1800 and 1899?]
Licence: Public Domain Mark
Credit: [The dwelling-house in relation to health : a lecture] / by Henry Simpson. Source: Wellcome Collection.
Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.
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![forms about one-fifth of the walls, will take up much more, bu1 put it at 5 per cent, which is really too low, and we have ioo,ooolb. of water, equal to 10,000 gallons, which must be got out of the walls before the house is fit to live in. Now, the only way if which this water can be got rid of is by the slow and gradual om of evaporation into the air, both of the rooms within the house and that outside. This drying of the walls can be made more rapid, as we al know practically, by the use of fires in the house. The air in oui climate is always charged with more or less moisture, and the quantity it can take up in an invisible form increases with the temperature. If therefore we have a fire in a room, the wall: of which are wet, we increase the quantity of vapour in the roonx and this vapour is given off from the wall. Supposing the venti lation of the room is pretty good, the heated air charged witl moisture escapes, and its place is taken by a fresh supply of air which, in its turn, takes up more of the moisture evaporating fron the wall, to be again carried away; and so the process of drying gradually goes on. Now when the walls of a house are thoroughly dried, so tha their pores, instead of being filled with water, are filled with air the moisture which is given off from the lungs and the skin o the inhabitants, and that produced by various domestic occu pations, as washing, cooking, &c., escapes into the outer air, beinj partly carried off by ventilation, and in part absorbed by the walli and passed gradually through them. In order that the latter par of the process may go on, it is necessary that the porosity of th( wall shall not be destroyed by any impervious covering such ai oil-paint or glass-paint, or by its pores being filled already witl water. The invisible moisture in a room is sometimes perceptible t( our unaided senses, though usually we think nothing about it, anc are unconscious of its presence; but as my friend Dr. Ransom( told you in his very interesting lecture on Pure Air, its present is easily shown if we condense it, and change its condition fron that of an invisible gas to that of a liquid or solid. To do thi we have only to mix snow, or powdered ice, with common salt ii a glass vessel, and the frozen moisture will soon be deposited 01 the outside of the glass. [£xjienme/iL] In a similar way : tumbler of water drawn from a deep well and brought at once int( a warm room will soon look dim, from the deposit of dew on thi outside of the glass. And when a thaw sets in after a few days frost, which has given time for walls to be thoroughly cooled, yoi will often have noticed that they become, especially if paintt j o](https://iiif.wellcomecollection.org/image/b21450365_0007.jp2/full/800%2C/0/default.jpg)
