8o 



Dentiphone. An instrument which, placed against the teeth, 

 conveys the sound to the auditory nerve. 



Depth Gauge. Any form of instrument for the measurement of 

 the depths indicated by sounding tubes in sea soundings. 

 [13, 15, 16, 21, 28.} 



Depth Recorder. A pneumatic instrument for the measuring and 

 recording of vertical depths in sea soundings. [13, 15, 16, 28.] 



Derniopathic Instrument. An acicular instrument used to 

 introduce a vesicatory beneath the skin. 



Detector Galvanometer. See Galvanometer. [10, 16.] 



Deviaplane. Enright's patent. An apparatus by which the 

 effect of sub-permanent magnetism and of magnetism 

 induced in iron beams and pillars can be indicated. [13.] 



Deviascope. A large model used at Board of Trade examination 

 rooms and in navigation schools for illustrating and teaching 

 the deviation of the compass in iron ships. [13, 15.] 



Deville's Theodolite. See Theodolite. [13, 20, 21, 25, 27.] 



Dewar Flask. A flask for keeping cold or hot liquids or solids 

 for long periods of time. It consists of a double-walled glass 

 vessel, the space between the two walls being exhausted of 

 air and the inner surface of the vacuum space being silvered. 



Diagometer. An electroscope, in which a dry pile is employed 

 to measure the amount of electricity transmitted by various 

 bodies, or to determine their conducting powers. 



Diagonal Eyepiece. See Eyepiece. [2. 3, 6, 9, 10, 11, 13, 15, 17, 

 18, 20, 24, 25.] 



Diagonal Scale. A mathematical scale, consisting of a set of 

 parallel lines drawn on a ruler, with other lines crossing 

 them at equal angles and at equal distances from each other. 

 [2, 5, 6, 15, 16, 17, 20, 21, 24, 25, 27.] 



Diagraph. A drawing instrument combining protractor and 

 scale. [13, 15, 20, 27.] 



Dial. Generally the scale or recording part of many instru- 

 ments, more particularly a sun-dial (q.v.). [9,13,15, 16, 17, 

 18, 20, 21, 24, 25, 27.] 



Dial, Azimuth. A dial whose style is at right angles to the 

 horizon. [13, 15, 16, 17, 20, 21, 24, 27, 28.] 



Dial, Hadley. An old form of Surveyor's dial. [13, 18, 21, 27.] 



Dial, Mining. A special form of magnetic compass, with sights, 

 used in underground surveying. [2, 5, 6, 13, 15, 16, 17, 18, 

 20, 21, 24, 25, 26, 27.] 



Dial, Refracting. A dial in which the reading of the hour is 

 viewed through some transparent, refracting fluid. [13.] 



Dial Sight. An instrument with a divided circle for reading 

 azimuth angles ; usually supplied as a panoramic periscope 

 used for indirect firing with artillery. [3, 9, 11, 13, 15, 16, 

 18, 20, 21, 27.] 



Dial 'Thermometer. See Thermometer. 



Dialling-Globe. An instrument for drawing all sorts of sun- 

 dials. 



