8 4 



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



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

 Drawing Fins. 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 Thermogalvanometer. See Thermogalvanometer. [4.] 

 Duddell Thermo-Ammeter. See Thenno-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. 



