Screws.—­In olden days the threads of a screw had to be filed out by hand, and the head struck up on the anvil.  The next step was to turn them in a lathe, but in 1849 a Gerimn clockmaker invented a machine by which females could make them five times as fast as the most skilful workman, and, as usual, the supply created a demand; the trade for a few years received many additions, and the “screw girders,” as the hard-working lasses were called, were to be met with in many parts of the town. 1852, 1,500 hands were employed, the output being from 20 to 25 tons per week, or 2,000,000 gross per year.  Gradually, however, by the introduction and patenting of many improvements in the machinery, the girls were, in a great measure, dispensed with, and their employers as well, Messrs. Nettlefold and Chamberlain having, in 1865, nearly the whole trade in their hands, and sending out 150,000 gross of screws per week.  Nearly 2,000 people are employed at Nettlefold’s, including women and girls, who feed and attend the screw and nail-making machines.  Notwithstanding the really complicated workings of the machines, the making of a screw seems to a casual visitor but a simple thing.  From a coil of wire a piece is cut of the right length by one machine, which roughly forms a head and passes it on to another, in which the blank has its head nicely shaped, shaved, and “nicked” by a revolving saw.  It than passes by an automatic feeder into the next machine where it is pointed and “wormed,” and sent to be shook clear of the “swaff” of shaving cut out for the worm.  Washing and polishing in revolving barrels precedes the examination of every single screw, a machine placing them one by one so that none can be missed sight of.  Most of the 2,000 machines in use are of American invention, but improved and extended, all machinery and tools of every description being made by the firm’s own workpeople.

Sewing Machines.—­The various improvements in these machines patented by Birmingham makers may be counted by the gross, and the machines sent out every year by the thousands.  The button-hole machine was the invention of Mr. Clements.

Sheathing Metal.—­In a newspaper called The World, dated April 16, 1791, was an advertisement beginning thus—­“By the King’s patent, tinned copper sheets and pipes manufactured and sold by Charles Wyatt, Birmingham, and at 19, Abchurch lane, London.”  It was particularly recommended for sheathing of ships, as the tin coating would prevent the corrosion of the copper and operate as “a preservative of the iron placed contiguous to it.”  Though an exceedingly clever man, and the son of one of Birmingham’s famed worthies, Mr. Charles Wyatt was not fortunate in many of his inventions, and his tinned copper brought him in neither silver nor gold.  What is now known as sheathing or “yellow” metal is a mixture of copper, zinc, and iron in certain defined proportions, according as it is “Muntz’s metal,”