n8 



Magnifier, Coddington. A magnifying glass composed of a 

 cylindrical lens with a deep groove cut in at an equal distance 

 from either end, acting as a diaphragm, giving good defini- 

 tion and wide field. [2, 3, 5, 9, 13, 15, 17, 20, 21, 22, 24, 

 25, 26, 27.] 



Magnifier, Triple Aplanat. A magnifier composed of two 

 meniscus lenses of flint glass separated by a double convex 

 lens of crown glass or similar construction. [1, 2, 3, 12, 13, 

 15, 22, 23, 26.} 



Magnifying Cursor. A slide-rule cursor with a magnifying lens 

 attached. See also Slide-Rule. [2, 6, 13, 17, 21, 24, 27.] 



Magnifying Glass. A convex glass or lens having the property 

 of magnifying the image of the object observed. [2, 3, 5, 

 13, 16, 17, 20, 21, 22, 24, 26, 27.] 



Magnophone. A microphone (q.v.). 



Mahler's Bomb Calorimeter. See Calorimeter. 



Mallock's Clinometer. See Clinometer. 



Mallock's Rolling Instrument. See Rolling Instrument. [13, 21.] 



Maltwood's Finder. A slide for the microscope, ruled in 

 numbered squares for registering and finding microscope 

 objects. [2, 3, 10, 20, 22, 26.] 



Mangin Mirror. See Mirror. 



Manoeuvring Boards. An instrument for the rapid graphical 

 solution of plane and spherical trigonometrical problems. 



Manometer. An instrument for measuring the tension or elastic 

 force of gases, steam, etc. ; constructed usually on the 

 principle of allowing the gas to exert its elastic force in 

 raising a column of mercury in an open tube, or in com- 

 pressing a portion of air or other gas in a closed tube with 

 mercury or other liquid intervening, or in bending a metallic 

 tube or spring so as to set in motion an index. A pressure 

 gauge. See also Gauge. [5, 6, 13, 15, 16, 17, 18, 21.] 



Manometer, Air. A sensitive form of pressure gauge to indicate 

 the pressure of the gas in the balloon of an airship. [4, 13, 

 15, 16, 17.] 



Manometer, Coal Dust. A manometer for recording the pressure 

 developed during an explosion of coal gas. [4.] 



Manometer, Differential. A manometer for indicating differences 

 of gaseous pressures, used in the measurement of the pressure 

 of furnace gas, etc. [6, 17.] 



Manometer, Flame. An instrument for obtaining graphic repre- 

 sentations of the sounds of the human voice. 



Manoscope. Strictly an instrument to indicate, but not to 

 measure, variations of gaseous pressure. Loosely used, the 

 term is the same as manometer (q.v.). 



Map Measurer. An instrument with a little wheel of known 

 circumference which is made to roll along a line and indicate 

 its length, the number of revolutions being counted. [2, 5, 

 6, 13, 15, 17, 20, 21, 24, 25, 26, 27.] 



