Drawing Pens. For the use of draughtsmen. [2, 5, 6, 9, 13, 15, 

 17, 20, 21, 24, 25, 26, 27.] 



Drawing Pins. For the use of draughtsmen. [2, 5, 6, 9, 13, 15, 

 17, 20, 21, 24, 25, 26, 27.] 



Drawing Scales. Mathematically divided scales for the use of 

 draughtsmen. [2, 5, 6, 9, 13, 15, 17, 20, 21, 24, 25, 26, 27.] 



Drawing Table. A mounted drawing board and stand for the 

 use of draughtsmen. [2, 5, 6, 9, 13, 15, 17, 20, 21, 24, 25, 

 27.] 



Dredge-Steward Omni-Telemeter. A form of portable telemeter 

 (q.v.) invented by the late Mr. W. Dredge. [13.] 



Drop Arrow. A special form of chain arrow for surveying on 

 hilly ground. [2, 6, 13, 15, 16, 17, 21, 24, 27.] 



Drop Shutter. See Shutter. [3, 20, 26] 



Drosometer. An instrument for measuring the quantity of dew 

 ,^,on the surface of a body in the open air. [13.] 



Dry Gauge. A gas pressure gauge which contains no liquid. [4. 

 17.] 



Ductilemeter. An instrument for accurately determining the 

 ductility of metals. 



Duddell Thennogalvanometer. See Thermogalvanometer. [4] 



Duddell Thermo-Ammeter. See Thermo-Ammeter. [4.] 



Duddell Oscillograph. See Oscillograph. [4] 



Dumb Plate or Dial. See Pelorus. [13, 15, 16.] 



Dumpy Level. See Level. [2, 5, 9, 10, 13, 15, 16, 17, 20, 21, 24, 

 25, 26, 27.] 



Dunbar-Scott Auxiliary Top and Side Telescope. An attachment 

 to the theodolite for plumbing or transferring bearings 

 down vertical or inclined shafts, or for taking any steep 

 sights which cannot be read by the main telescope. [2, 5, 6, 

 9, 10, 13, 15, 16, 17, 20, 21, 24, 25, 26, 27.] 



Duplex Gauge. See Gauge. 



Duplex Standard Test-Gauge. See Test-Gauge. [5, 13, 15, 17, 28.] 



Dust-Counter, Aitken's. An instrument for determining the 

 amount ot dust in any atmosphere. It operates by the 

 dust particles acting as nuclei for condensation. 



Dynactinometer. An instrument for measuring the intensity of 

 the photogenic (light-producing) rays and computing the 

 power of object-glasses. 



Dynameter. An instrument for determining the magnifying 

 power of telescopes. It usually consists of a micrometer 

 applied to the eye end of a telescope for measuring accur- 

 ately the diameter of the emergent pencil of light. [2, 3, 

 17, 21, 25, 26] 



Dynamograph. A recording dynamometer. 



Dynamometer. An apparatus for the measurement of force, 

 especially muscular effort of men or animals, or the force 

 exerted by a motor, or that required to operate machinery. 



