126 



Monochord. An instrument consisting of a wood frame fitted 

 with one or more steel wires and movable bridges, and an 

 arrangement for varying the tension of the wires, used for 

 experiments in sound vibrations. See Sonometer. 

 Monochromatic Bench. An optical bench for producing mono- 

 chromatic light. [2, 3, 26.} 



Monochromatic Lamp. A lamp fed with a mixture of a solution 

 of common salt and alcohol, or other lamp for producing 

 monochromatic light. [26.} 

 Monochromator. A lamp giving illumination from one part of 



the spectrum ; another name for a spectroscope. [14.] 

 Monocle. A single eyeglass. [10, 17, 20, 21, 26} 

 Mooney's Rhumboscope. See Rhumboscope. [15.} 

 Morrow's Mirror Extensometer. See Extensometer. 

 Morsaphore. A special pattern of ship's semaphore combined 



with a Morse signalling lamp. [13, 15, 16.] 

 Morse Lamp. A special lamp for signalling by the Morse code. 



[13, 15, 16, 26, 28} 



Morse Tapper. A telegraphic key or instrument for producing 

 the dot and dash signals in telegraphy. [15, 16, 17, 19, 28} 

 Motor-Car Gauges. Various gauges made for and used on motor- 

 cars for determining speed, gradient, etc. [13, 17.] 

 Mountain Barometer. A portable barometer (q.v.) designed for 

 measuring vertical heights above the sea. [2, 5, 6, 13, 15, 

 16, 17, 20, 21, 24, 25, 26, 27, 28} 

 Mountain Rain-Gauge. See Rain-Gauge. [6, 13, 15, 17, 20, 21, 



24, 25, 26} 

 Mountain Transit Theodolite. See Theodolite. [2, 6, 13, 17, 21, 



24, 25, 26, 27.] 



Moving Magnet Galvanometer. See Galvanometer. [4, 10, 16, 19} 

 Multiplex Slide-Rule. See Slide-Rule. [13, 21, 26} 

 Multiplicator. In galvanometers, a flat coil of conducting wire 

 for multiplying the effect of the current upon the needle. 

 Munro Air-Speed Indicator. See Speedometer. [15.] 

 Muralcircle. A graduated circle on the plane of the meridian 

 attached permanently to a perpendicular wall, used for 

 measuring arcs of the meridian. 

 Mydriasis Spectacles. See Spectacles. [26} 

 Mydynamometer. An instrument for measuring the muscular 



strength of a man or other animals. 



Myograph. An instrument for determining and recording 

 different phases, such as the intensity and velocity of a 

 muscular contraction. See also Pendulum Myograph. [4.] 

 Myrioscope. A form of kaleidoscope (q.v.). [20.] 



Nachet's Prism. See Prism. [2, 3, 26} 



Napier's Compasses. A draughtsman's folding pocket-compasses, 

 to one leg of which is pivoted a plain point and pencil- 

 holder and to the other a plain point and pen. See 

 Compasses. [2, 5, 6, 13, 15, 17, 20, 21, 24, 25, 26, 27, 28} 



