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EXPOSITION AT VIENNA.
interior and exterior surfaces of walls, so as to exclude dampness and secure greater warmth. This is of great importance, and especially where "furring off” the wall is avoided, as it should he for many good reasons. But the great cause of dampness, and consequent great conducting power of walls, is not likely to be avoided by even hollow brick of the best construction, unless access of water to the outside and the foundations is prevented by impervious materials. The capillary power of raising water in walls is well known, particularly in Paris, where dampness has been observed to rise thirty-two feet above the foundations. Long, driving rains fully saturate brick walls and chimneys, and exudations of water are found inside of dwellings about chimneys where no leak can be discovered. The capacity of »absorption of water by bricks is probably not less than a pint to each one. Mr. Chadwick, in his " Report on Dwellings for the Poor,” says that in England common bricks absorb as much as a pint or pound of water; and supposes a case of a cottage wall consisting of twelve thousand bricks, which would be capable of holding fifteen hundred gallons, or six and a half tons of water when saturated. To evaporate this would require a ton of coal. Sandstone and granite also hold quantities of water in their pores. Prof. Ansted states that granite, in a dry state, is rarely without a pint and a half of water in each cubic foot. Sandstone may contain half a gallon, and loose sand two gallons.
The absorptive capacity of bricks varies with their density, depending upon'the process of manufacture. This has been shown by Cyrus Chambers, in experiments upon bricks made by the machine of his invention and on handmade bricks, the results of which are given in the annexed table :—