the joining and fastening together of two pieces of the same metal, or of two different metals, by the fusion and application of some metallic composition on the extremities of the metals to be joined.

To folder upon silver, brads, or iron : Take silver, five pennyweights; brads, four pennyweights: melt them together for soft folder, which runs soonest. Take silver, five pennyweights; copper, three pennyweights: melt them together for hard folder. Beat the folder thin, and lay it on the place to be foldered, which must be first fitted and bound together with wire as occasion requires; then take borax in powder, and temper it like pap, and lay it upon the folder, letting it dry; then cover it with live coals, and blow, and it will run immediately; take it presently out of the fire, and it is done. It is to be observed, that if any thing is to be foldered in two places, which cannot well be done at one time, you must first folder with the harder folder, and then with the soft; for if it be first done with the soft, it will unfold again before the other is fastened. Let it be observed, that if you would not have your folder run about the piece that is to be foldered, you must rub such places over with chalk.—In the foldering either of gold, silver, copper, or either of the metals above mentioned, there is generally used borax in powder, and sometimes rosin. As to iron, it is sufficient that it be heated red hot, and the two extremities thus hammered together, by which means they will become incorporated with each other. For the finer kinds of iron and steel instruments, however, gold proves an excellent folder. This metal will dissolve twice or thrice its weight of iron in a degree of heat very far less than that in which iron itself melts; hence if a small plate of gold is warped round the parts to be joined, and afterwards melted by a blow-pipe, it strongly unites the pieces together without any injury to the instrument, however delicate.