Cholera : how to prevent and resist it / by Max von Pettenkofer.

  • Max Joseph von Pettenkofer
Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: Cholera : how to prevent and resist it / by Max von Pettenkofer. Source: Wellcome Collection.

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    9 air; and the interspaces between tlie stones may become filled with water, or any kind of gas, as well as air. Even far more compact substances tlian gravel contain within them pores whose combined volume forms a consider- able part of the wliole mass. For instance, I have found tbat new, well-baked bricks will absorb as much as half a pint ot water; a compact sandstone, suitable for building purposes, will in a short time absorb from live to six per cent. of its own weight of water.* The water of course can only penetrate into the open spaces wliich exist in the solid material. The large quantity of water which can be absorbed will give some idea of the extent of the pores, and of the sort of honeycomb material of which the walls of our houses are bnilt. The following experiments, devised by Prof, von Pettenkofer illustrate the above remarks in a striking manner. The first illustration represents a cylinder of solid dry mortar, 5 inches by 1'. It is covered with wax, except at the ends, and to each of these ends is attached, by means of wax, afunnel which termi- nates in a tube. By blowing through one tube, even though no great eflort be mkde, it will be found that the breath will pass through the solid mortar with sufficient force to blow aside the flame of a candle held near the opposite tube. A block of apparently solid gravel contains one-third as much air as stone, and a house built on such a foundation is therefore practically resting on a stone support which Stands in air. * Thia is tme of a fine hard sandstone extensively used for building in Sheffield. A block of it measuring 5 in. by 5 in. by 2i in. high, weighing when dry C lb., will absorb 4 to 41 <>'/.. of water in a few hours.
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