A new system of practical domestic economy.

Date:
1823
Catalogue details

Licence: Public Domain Mark

Credit: A new system of practical domestic economy. Source: Wellcome Collection.

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    readily, when it is applied to their surface, and therefore seldom present the appearance of damp walls, as in stone buildings, except where the mor- tar has been injudiciously mixed with sea-sand. We speak not, however, of the modern London bricks. They are of most perishable materials, like many others which may be seen to decay ra- pidly when exposed to the air, covered with a white efflorescence which chemistry shews to be a sulphat of magnesia, arising from some species of clay abounding in their composition, and very sus- ceptible of atmospheric influence. Some persons consider stone as the only or- namental material, and where first expense is no object, there will certainly be an ultimate saving from its use; but then whenever it is employed, it ought to be well ascertained to be capable of re- sisting both air and water. It is true, indeed, that stone in England is not so permeable to water as in other countries. In Bermuda, for instance, where the stone is a species of filter, a new house bears no proportionate value to an old one of the same size, whose walls have been saturated with repeatedwhite-washings for a number of years, so as to have acquired an artificial impermeability. With us, however, several species of stone, exposed to the air, are rapidly destructible, sometimes crumbling to powder, although extremely hard when first dug from the quarry. In this class are all those stones which abound with clay, or alu- mine, which has so great an affinity for water as to absorb moisture from the air to the extent of de- stroying its own aggregation. Other species again lose their aggregation by an opposite cause; such as marbles of particular kinds, also crystallized car- bonates of lime, or stones composed of an acid and earth combined with water, called the water of
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