[Illustration: Egyptian labour in the brick-field.] There is another material for building which was little used at the beginning of the century. The consumption of slate in London alone was, in 1851, from thirty thousand to forty thousand tons per annum. The quarries of Wales principally supply this immense quantity; but some slates are shipped from Lancashire and Westmorland, and from Scotland and Ireland. In the production of this one material, eight thousand quarriers are employed in Great Britain. Slates are not only used for roofing houses, but in slabs for cisterns and chimney-pieces. The great increase of the supply of water to houses by machinery led to a demand for a safer and cheaper material than lead for cisterns; and slate supplied the want. How great a variety of things are contained in an ironmonger's shop! Half his store consists of tools of one sort or another to save labour; and the other half consists of articles of convenience or elegance most perfectly adapted to every possible want of the builder or the maker of furniture. The uncivilized man is delighted when he obtains a nail,--any nail. A carpenter and joiner, who supply the wants of a highly civilized community, are not satisfied unless they have a choice of nails, from the finest brad to the largest clasp-nail. A savage thinks a nail will hold two pieces of wood together more completely than anything else in the world. It is seldom, however, that he can afford to put it to such a use. If it is large enough, he makes it into a chisel. An English joiner knows that screws will do the work more perfectly in some cases than any nail; and therefore we have as great a variety of screws as of nails. The commonest house built in England has hinges, and locks, and bolts. A great number are finished with ornamented knobs to door-handles, with bells and bell-pulls, and a thousand other things that have grown up into necessities, because they save domestic labour, and add to domestic comfort. And many of these things really are necessities. M. Say, a French writer, gives us an example of this; and as his story is an amusing one, besides having a moral, we may as well copy it:--