Page:On the economy of machinery and manufactures - Babbage - 1846.djvu/176

142 to one-fourth or one-fifth of their present price, he would still have an interest in procuring the best drugs, for the sake of his own reputation or skill. Or if the medical attendant, who is paid more highly for his time, were to have several pupils, he might himself supply the medicines without a specific charge, and his pupils would derive improvement from compounding them, as well as from examining the purity of the drugs he would purchase. The public would gain several advantages by this arrangement. In the first place, it would be greatly for the interest of the medical practitioner to have the best drugs; it would be his interest also not to give more physic than needful; and it would enable him, through some of his more advanced pupils, to watch more frequently the changes of any malady.

(190.) There are many articles of hardware which it is impossible for the purchaser to verify at the time of purchase, or even afterwards, without defacing them. Plated harness and coach furniture may be adduced as examples: these are usually of wrought iron covered with silver, owing their strength to the one and a certain degree of permanent beauty to the other metal. Both qualities are, occasionally, much impaired by substituting cast for wrought iron, and by plating with soft solder (tin and lead) instead of with hard solder (silver and brass). The loss of strength is the greatest evil in this case; for cast iron, though made for this purpose more tough than usual by careful annealing, is still much weaker than wrought iron, and serious accidents often arise from harness giving way. In plating with soft solder, a very thin plate of silver is made to cover the