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Planimeter, Coffin Averaging. A planimeter for working out 

 indicator diagrams. [10, 13, 15, 16, 21, 24, 28.] 



Planisphere. An instrument to assist in the study of the posi- 

 tions of the heavenly bodies. [13, 15, 16, 20.] 



Plank Rule. A sliding boxwood calliper (q.v.) used for ascer- 

 taining the width and thickness of planks. [15.] 



Planoineter. An instrument for gauging or testing a plane 

 surface. 



Platinum Resistance Pyrometer. See Pyrometer. [4.] 



Platometer. An instrument for measuring areas on plans by 

 mechanism. See also Planimeter. [2, 5, 6, 10, 13, 15, 16, 

 17, 21, 24, 25, 27.] 



Platymeter. An apparatus for measuring the inductive capacity 

 of dielectrics. 



Plethmograph. An instrument for determining and registering 

 the variations in the size of a limb, as the arm or leg, and 

 thence the variations of the amount of blood in the limb. 



Pleximeter. A small hard elastic plate, as of ivory, bone, or 

 rubber, placed in contact with the body to receive the blow 

 in examination by medical percussion. 



Plumb Bob. A conoidally or other shaped piece of metal sus- 

 pended by a cord attached to its upper end and used for 

 determining vertical, or, in connection with a level or straight 

 edge, horizontal lines. See also Plumb Level. [2, 5, 16, 17, 

 21, 24, 25, 26, 27.] 



Pluviograph. A self-recording lain-gauge (q.v.). [13, 17, 20, 27.] 



Pluviometer. An instrument for ascertaining the amount of 

 rainfall in a particular climate or place. See also Rain- 

 Gauge. [6, 13, 15, 17, 20, 25, 27.] 



Pneometer. A spirometer (q.v.). 



Pocket Compasses. Magnetic compasses that may be placed in 

 the pocket. See Compasses. [2, 5, 9, 13, 15, 16, 17, 20, 21, 

 24, 26, 27.] 



Pocket Dividers. Folding dividers that may be placed in the 

 pocket. See Dividers. [2, 5, 9, 13, 15, 16, 17, 20, 21, 24, 

 26, 27.] 



Polar Clock. An optical instrument, invented by Wheatstone, 

 for ascertaining the time of day by means of polarised light. 



Polar Planimeter. See Planimeter. [2, 13, 15, 21, 24, 27.] 



Polarimeter. An instrument for measuring the rotation of the 

 plane of polarisation in polarised light. [2, 13, 14, 15, 17, 

 21, 26.] 



Polariser. A crystal, such as tourmaline or calcite, producing 

 polarised light. See Tourmaline Analyser. [3, 26.] 



Polarising Apparatus. Any instrument for producing polarised 

 light. [2, 3, 16, 17, 20, 22, 26.] 



Polariscope. An instrument consisting essentially of a polariser 

 and an analyser used for polarising light and analysing its 

 qualities. See also Saccharimeter. [2, 3, 14, 15, 17, 19, 20, 

 21, 22, 26.] 



