198.  Articles become old from actual decay, or the wearing out of their parts; from improved modes of constructing them; or from changes in their form and fashion, required by the varying taste of the age.  In the two latter cases, their utility is but little diminished; and, being less sought after by those who have hitherto employed them, they are sold at a reduced price to a class of society rather below that of their former possessors.  Many articles of furniture, such as well-made tables and chairs, are thus found in the rooms of those who would have been quite unable to have purchased them when new; and we find constantly, even in the houses of the more opulent, large looking-glasses which have passed successively through the hands of several possessors, changing only the fashion of their frames; and in some instances even this alteration is omitted, an additional coat of gilding saving them from the character of being second-hand.  Thus a taste for luxuries is propagated downwards in society’, and, after a short period, the numbers who have acquired new wants become sufficient to excite the ingenuity of the manufacturer to reduce the cost of supplying them, whilst he is himself benefited by the extended scale of demand.

199.  There is a peculiarity in looking-glasses with reference to the principle just mentioned.  The most frequent occasion of injury to them arises from accidental violence; and the peculiarity is, that, unlike most other articles, when broken they are still of some value.  If a large mirror is accidentally cracked, it is immediately cut into two or more smaller ones, each of which may be perfect.  If the degree of violence is so great as to break it into many fragments, these smaller pieces may be cut into squares for dressing-glasses; and if the silvering is injured, it can either be resilvered or used as plate-glass for glazing windows.  The addition from our manufactories to the stock of plate-glass in the country is annually about two hundred and fifty thousand square feet.  It would be very difficult to estimate the quantity annually destroyed or exported, but it is probably small; and the effect of these continual additions is seen in the diminished price and increased consumption of the article.  Almost all the better order of shop fronts are now glazed with it.  If it were quite indestructible, the price would continually diminish; and unless an increased demand arose from new uses, or from a greater number of customers, a single manufactory, unchecked by competition, would ultimately be compelled to shut up, driven out of the market by the permanance of its own productions.

200.  The metals are in some degree permanent, although several of them are employed in such forms that they are ultimately lost.

Copper is a metal of which a great proportion returns to use:  a part of that employed in sheathing ships and covering houses is lost from corrosion; but the rest is generally remelted.  Some is lost in small brass articles, and some is consumed in the formation of salts, Roman vitriol (sulphate of copper), verdigris (acetate of copper), and verditer.