A considerable number of other mechanisms are termed indicators, as the stock-indicator, a receiving telegraph instrument that prints on an endless tape the figures, etc., of stock sales telegraphed; telegraph indicator, a telegraphic instrument having a vertical needle making in dications on a dial, called also needle telegraph; circuit indicator, an upright galvanometer or the like for indicating the presence and char acter of an electric current; speed indicator, a gauge having usually a dial and pointer for in dicating visually the speed of a machine, etc.; track-indicator, a registering device for mount ing on a railway car or locomotive to record the variations of the track from accurate level and alignment.
For detailed information concerning the steam-engine indicator and its uses, consult Pray,
a period or cycle of IS years.
The ongin of indiction as a chronological period is not known. Several writers have propounded theories explanatory of its origin, none of which are supported by any evidence. In the time of Athanasius it came into favor among ecclesiastical writers. Being adopted by the Popes, it came into general use during the Middle Ages. The time from which reckoning by indictions began is, according to some, 15 Sept. 312; according to others, 1 Sept. 312; but when this method was adopted by the Popes, It was ordered to be reckoned as beginning l Jan. 313. The latter only is now used, and is called the Papal Indiction. If we reckon back ward to the beginning of the Christian era, it will be found that 1 A.D. corresponds to the fourth year of an indiction— hence, if to any given year of the Christian era three he added., and the sum divided by 15, the remainder will give the position of that year in an indiction— e.g., 1918 was the first year of the 108th Papal Indiction.