The medical aspects of Bournemouth and its surroundings / Horace Dobell ; illustrated with chromolithographs (by Hanhart), and photographs (by Debenham and Gould), from original sketches by the author.

  • Dobell, Horace, 1828-1917.
Date:
1886
Catalogue details

Licence: Public Domain Mark

Credit: The medical aspects of Bournemouth and its surroundings / Horace Dobell ; illustrated with chromolithographs (by Hanhart), and photographs (by Debenham and Gould), from original sketches by the author. 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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    ' The measure of dampness then is the nearness of the amount of the watery vapour, which, more or less, is always present in the atmosphere, to the point at which it begins to be pre- cipitated in a sensible shape. Consequently, the greater the removal from the point of saturation, the greater the dry- ness. The point of saturation is the dew-point. Hence the distance between the temperature of the air and the tem- perature of the dew-point is the measure of sensible dryness [e.g., if the temperature of air is 60° and the dew-point 60°, there is complete saturation; if the temperature of the air is 60° and dew-point 50°, there are 10 of dryness], An air with ten degrees between the two is therefore drier than an air with nine degrees, or any smaller number. But the sensible dryness is not always a measure of the real dry- ness. In a hard frost the air may be saturated with moisture, but from its low temperature if is a much drier air in its effects upon our bodies, owing to the circumstance that it requires to be much more warmed up when in contact with either skin or lungs than usual; and therefore the humidity which satu- rated it when at 32° is far from doing so when it has been raised up to 98°, our natural temperature. Hence a fi-osty air, though saturated with moisture, is always a dry air, whilst summer air, which is not near to the poiut of satura- tion, is a much moister air, though its moisture is in a latent form. Consequently a place may, from being more uniformly warm, contain more latent humidity in its air, and yet possess a drier air, as regards freedom from damp or sensible moisture, than another which shall be damper, and yet possess less of actual humidity in the atmosphere. The sensible dryness is measured by the number of degrees of difference between the mean temperature of the air and the mean temperature of the dew-point. The actual amount of latent Immidity contained in the air is measured by the number of degrees at which the dew-point stands. When the dew-point is high, the quantity of latent hu- midity is great, whatever the sensible dryness may be. TFhen