(photography, historical) A photographic process based on the action of light in rendering a thin layer of bitumen, with which the plate is coated, insoluble.

(engineering, mining) A method of sinking through water-bearing ground, in which the shaft is lined with tubbing and provided with an airlock, work being proceeded with under air pressure.

A process of electric welding in which heat is developed by a large current passing through the metal.

A process by which copper matte is treated by passing through it a blast of air, to oxidize and remove sulphur. It is analogous in apparatus to the process of making Bessemer steel.

A process of desilverizing argentiferous lead by repeated meltings and skimmings, which concentrate the silver in the molten bath, the final skimmings being nearly pure lead.

A process of tanning goatskin, calfskin or sheepskin, with a combination of vegetable and mineral agents, so that it resembles kid leather.

The process of treating silver ores by grinding in pans or tubs with the addition of mercury, and sometimes of chemicals such as blue vitriol and salt.

A process for hardening the face of steel, involving the additional carburizing of the face of a piece of low-carbon steel by heaping a solid carbon-rich fuel (such as charcoal) on the face of the steel and then subjecting this to very high heat at high pressure for a prolonged period of time, followed by a violent chilling, as by a spray of cold water. This results in a thick surface of extreme hardness supported by material gradually decreasing in hardness to the unaltered soft steel at the back.

(metalworking) A process of extracting gold or silver by treating the ore in a revolving barrel or drum, with mercury, chlorine, cyanide solution, or other reagent.

(metalworking) A Bessemer process or open-hearth steel-making process in which a lining that is basic, or not siliceous, is used, and additions of basic material are made to the molten charge during treatment.