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.] 

 Dermopathic 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. 



