The power of existing in several modifications possessed by some substances, notably by chemical elements. Instances of the allotropic state are found in carbon which exists as charcoal, as graphite (plumbago or black lead), and as the diamond. All three are the same elemental substance, although differing in every physical and electrical property.

The placing in or occupying of the same straight line. The bearings of a shaft in dynamos, engines, and other machinery have to be in accurate alignment.

A current of electricity passed through impure alcohol between zinc electrodes is found to improve its quality. This it does by decomposing the water present. The nascent hydrogen combines with the aldehydes, converting them into alcohols while the oxygen combines with the zinc electrode.

An alarm operated by a change of water level in a tank or boiler. By a float a contact is made as it rises with the water. Another float may be arranged to fall and close a contact as the level falls. The closing of the contacts rings an electric bell to notify the attendant [...]

An alarm to indicate an overflow of water has been suggested on the lines of a contact completed by water, or of the elements of a battery which would be made active by water. Thus two sheets of metal might be separated by bibulous paper charged with salt. If these sheets were terminals of a [...]

An alarm for giving notice of the existence of a conflagration. Such are sometimes operated by a compound bar thermostat (see Thermostat), which on a given elevation of temperature closes a circuit and rings an electric bell. Sometimes the expansion of a column of mercury when heated is used. This, by coming in contact with [...]

An appliance for calling attention, generally by ringing a bell. It is used to notify of water-level in boilers or tanks, of entrance of a house, or of other things as desired. It is evident that any number of alarms could be contrived.

A system of circuits with alarm bell extending over a house or apartments designed to give notice of the opening of a window or door. As adjuncts to the system the treads of the stairs are sometimes arranged to ring the bell, by completing a circuit when trod on. Door mats are also arranged to [...]

A mercurial air pump in which the fall of mercury or the height of the active column is comparatively small. It is effected by using several columns, one acting after the other. A height of ten inches for each column suffices in some forms. Enough columns must be used in succession to make up an [...]

An air pump operated by mercury. The mercury acts virtually as the piston, and the actuating force is the weight of the column of mercury, which must exceed thirty inches in height. There are many types. Mercurial air pumps are largely used for exhausting incandescent lamp chambers. (See Geissler Air Pump,–Sprengel Air Pump.)