Machine-making on a large scale is carried on by firms widely celebrated for the construction of locomotives, railway trucks and carriages, steamboilers and motors, turbines, pumps, metal bridges and roofs.
The explanation of this would seem to lie in the fact that the relics are in most cases the paraphernalia of tombs, the funereal vessels and vases, and iron being considered an impure metal by the ancient Egyptians it was never used in their manufacture of these or for any religious purposes.
Each of these ancient processes thus consists essentially in so manipulating the temperature that, out of the several possible constituents, the metal shall actually consist of a special set in special proportions.
The chief industry of Cambrai is the weaving of muslin (batiste) and other fine fabrics (see Cambric); wool-spinning and weaving, bleaching and dyeing, are carried on, as well as the manufacture of chicory, oil, soap, sausages and metal boxes.
In the surface of the metal the workman cuts grooves wider at the base than at the top, and then hammers into them gold or silver wire.
A freshly prepared surface of the metal closely resembles zinc in appearance, but on exposure to the air it rapidly tarnishes, becoming yellowish and ultimately grey or white in colour owing to the formation of a surface layer of calcium hydrate.
The variation of physical properties which attends iron on heating has led to the view that the metal exists in allotropic forms (See Iron And Steel, below).
When a pure metal is cooled to a very low temperature its electrical conductivity is greatly increased, but this is not the case with an alloy.
When mixed with sodium carbonate and heated on charcoal in the reducing flame lead salts yield malleable globules of metal and a yellow oxide-ring.
Of the several products, the chlorides of gold and platinum (AuC13 and PtC1 4) are the only ones which when heated beyond their temperature of formation dissociate into metal and chlorine.