The manufacture of springs, valves and washers does not require any very special notice, these articles being generally fashioned out of mixed rubber, and vulcanized either in moulds or in powdered French chalk.
Flanged joints are made to bolt together on washers of vulcanized rubber.
These vessels, as well as all others which are used in the process, are not open to the air, but communicate with it through washers in which fresh salt solution is employed for retaining any escaping vapours of ammonia.
The kilns are closed at the top, and the gases are drawn out by powerful air-pumps, washers being interposed be,, veen the kilns and the pumps for the purpose of purifying and cooling the gas.
Every winter the supply is exhausted by the washers, and every summer it is renewed by the river.