l62 



Stereoscopic Telescope. See Telescope. [2, 3, 13, 20, 26.] 

 Stethometer. A surgical instrument for measuring the external 



movement in the walls of the chest during respiration, as 



a means of diagnosis in thoracic disease. 

 Stethoscope. An instrument employed in auscultation for 



testing the pulsation of the heart and lungs, etc. [2, 26.] 

 Stevenson Screen. A stand and screen for out-door thermo- 

 meters. [2, 6, 13, 15, 17, 21, 24.] 

 Stigmatic. An anastigmat lens (q.v.) having an aperture of / 6. 



The single components are corrected and can be used alone, 



giving increased focal lengths. 

 Stokes's Colorimeter. See Colorimeter. 

 Stomatoscope. An instrument for keeping the mouth open for 



purposes of inspection. 

 Stonyhurst Sun-Discs. Specially designed discs for measuring 



the position of sunspots. [2, 6.] 

 Storage Cell. See Accumulator. 

 Strabismometer. An instrument for measuring the amount of 



strabismus. [26.] 

 Straight-Edge. A ruler with edge truly aligned. [2, 5, 6, 13, 



15, 16, 17, 20, 21, 24, 25, 26, 27] 



Straight-Stem Thermometer. See Thermometer. [5, 6, 13, 15, 



16, 17, 21.] 



Strain-Measurer. An apparatus designed to measure directly 

 the strains to which the different parts of any structure are 

 subjected. 



Stroboscope. (i) An instrument for studying or observing the 

 successive phases of a periodic or varying motion by means 

 of light which is periodically interrupted. (2) An optical 

 toy. 



Stytometer. An instrument for measuring columns. 



Submarine Camera. A special form of camera (q.v.) for use under 

 water for submarine photography. [16.] 



Submarine Sentry, James. A special form of sounding machine 

 (q.v.) consisting of a " kite " which is towed after the vessel 

 and, from its construction, submerges and remains at a 

 constant depth below the water. Should the vessel pass 

 into shallow water the trigger, on touching the bottom, is 

 dislodged and the kite rises to the surface, sounding a bell 

 or gong on board. [13, 15, 17, 28] 



Submarine Telescope. See Telescope. [13, 15.] 



Subsidence Apparatus. An apparatus for investigating the slow 

 subsidence of a building, etc., or the progress of the effect 

 of a geological fault. [4] 



Substance Diaphragm. The telescope diaphragm of surveying 

 instrument used to measure distances. [21.] 



Sugar-Boiling Thermometer. See Thermometer. [5, 6, 13, 15, 

 16, 17, 21.] 



Sulphur Apparatus. Apparatus for testing the purity of coal gas. 



