56 



Aneroid. See Barometer. [2, 3, 5, 6, 13, 15, 16, 17, 20, 21, 24, 



25, 26, 27, 28.] 



Aneroidograph. A self-recording aneroid barometer. 

 Anglemeter. An instrument used by geologists to measure the 



dip of strata. [17, ] 

 Angle Mirror. See Optical Square. [2, 11, 13, 15, 17, 21, 24, 



25, 27.] 



Angle-of-Sight Instrument. An instrument for measuring the 



angle with the horizon which an object subtends at the eye. 



It consists of a spirit-level and an adjustable sighting 



apparatus. [2, 3, 6, 13, 15, 18, 20, 25, 26, 27.] 

 Angleometer. An instrument for measuring external angles. 



[13, 15, 17.] 

 Angle Sextant. A special form of sextant used on ships for 



quickly measuring horizontal or shore angles. [6, 13, 15, 



16, 17, 25, 27.] 



Angstrom's Compensation Pyrheliometer. See Pyrheliometer. 

 Anorthoscope. An optical toy for producing pictures by means 



of two revolving discs. 

 Anthrocometer. An instrument for measuring the carbonic acid 



in a mixture. 

 Anthropometric Apparatus. Instruments designed for testing 



and measuring the chief physical and some mental charac- 

 teristics of the human subject. 

 Antimeter. A modification of the quadrant for measuring small 



angles. 

 Apertometer. An optical arrangement for measuring the 



numerical and angular aperture of a lens, especially of a 



microscope objective. [2, 3, 20, 26.] 

 Aphengoscope. A modification of the magic lantern, for 



exhibiting opaque objects. [2, 3, 17, 20, 26.] 

 Aplanatic Lens. See Lens. \1, 2, 3, 8, 9, 10, 17, 20, 21, 22, 23, 



26, 27.] 



Aplanatic Magnifier. See Magnifier. [1, 2, 3, 9, 10, 15, 17, 20, 



21, 22, 25, 26, 27.] 



Apochromatic Condenser. See Condenser. [2, 3, 20, 22, 26] 

 Apochromatic Object-Glass. See Object-Glass. [2, 3, 8, 20, 22, 



26] 

 Apomecometer. An instrument for measuring the heights of 



objects at a distance, e.g., trees, buildings, etc. [15, 21.] 

 Apophorometer. An instrument enabling sublimates obtained 



from substances at high temperatures to be collected in 



their entirety and weighed. [4.] 

 Architects' Scales. Scales made of ivory, boxwood, or celluloid, 



and graduated for use by architects for drawing and 



designing. [2, 5, 6, 15, 16, 17, 20, 21, 24, 25, 27] 

 Arcograph. An instrument for describing an arc of a circle 



without the use of a central point ; a cyclograph or curvo- 



graph. [27] 



