86 



Elacometer. An apparatus for determining the amount of oil 

 contained in any substance, or for ascertaining the degree 

 of purity of oil. 



Elatrometer. An instrument for measuring the degree of 

 rarefaction of air contained in the receiver of an air-pump. 



Electric Alarm. A form of electric bell or other sounder some- 

 times used in connection with a thermostat, for giving an 

 alarm when the temperature rises to a point at which the 

 instrument recording the temperature completes the circuit. 

 [4, 6, 16, 21.] 



Electric Balance. An instrument used for determining the 

 value of electrical balance by employing the force between 

 neighbouring coils through which the current flows. [16, 19.] 



Electric Battery. A series of voltaic cells or of Leyden jars 

 connected in series or in parallel to yield an electric current. 



Electric Clock. A dial with hands and gong-train impelled by 

 recurrent impulses from an electromagnet. [10, 16, 17.] 



Electric Furnace, Lessing's. An electric furnace for the deter- 

 mination of the coking properties of coal. 



Electric Signal Timing Clock. Designed to give an automatic 

 electric bell signal for timing observations in laboratory and 

 other work. [10, 18.] 



Electric Slide-Rule. A special form for electric calculations. [IS.] 



Electric Thermostat. See Thermostat. [4, 13] 



Electrical Distance-Pyrometer. See Pyrometer. [6, 13, 16.] 



Electrical Distance Thermometer. See Thermometer. [4, 6, 13, 

 16.] 



Electrical Locomotive Pyrometer. See Pyrometer. [4, 13, 16] 



Electro-Calorimeter. See Calorimeter. [19] 



Electro-Cardiograph. An instrument used in the study of heart 

 affections, enabling the records to be obtained of the minute 

 electric currents produced by the action of the heart, by 

 means of a string galvanometer (q.v.) and photographic 

 recording apparatus. [21] 



Electro-Chronograph. An instrument for recording time and 

 events in the instant and order of their occurrence, as in 

 the notation of transits in observatories. [4, 13, 15, 16, 17, 

 21, 24, 25, 27, 28] 



Electroergometer. An instrument for measuring the work done 

 in an electric circuit or part thereof. 



Electro-Magnet. See Magnet. 



Electrometer. An instrument for measuring differences of 

 electrical potential. [4, 16, 19.] 



Electrometer, Balance. An electrometer in which the electro- 

 static attraction between two plates is measured by means 

 of a simple balance arm. [16] 



Electrometer, Capillary, Lippmann's. An electrometer in which 

 electric potential differences are measured by variations in 

 the surface tension of a liquid, usually mercury, contained 

 in a capillary "tube. 



