36 GENERAL INDEX. 



Page 



Polarised tints, their deviation from Newton's scale . . . POLAR. OF LIGHT , 32 



Polai'ising intensities of different crystal*, table of . . . 31 



Poles, virtual, of the rings of topaz " . . . . _ . . 33 



Position proper for the sails of a windmill . . . . MECHANICS, t. i. . 25 



of the optic axis for different coloured rings . . POLAR. OF LIGHT . 32 



Positive and negative axes of refraction . . . . , .. _ , 2 



... systems of coloured rings . . . . 21 



Power of the pressure of water . . . . . . HYDROSTATICS . 7 



requisite to work pumps . . . . . . HYDRAULICS . 21 



of conducting heat in different sorts of wood . . . HEAT . . .22 



of fluids . . ... 25 



and weight distinguished . . . . . MECHANICS, t. ii. . 1 



illuminating, of the prismatic spectrum OPTICS . . 29 



magnetizing, of the solar rays ..... . . .29 



Powers, mechanical, described . % . . . . PREL. TREAT. 18. MECH. ii. 8 



.. refractive of non-transparent bodies, method of measuring POLAR. OF LIGHT . 12 



Practical mechanics, denned and illustrated . . . . PRELIMINARY TREAT. 17 



Prediction of the weather by the barometer, rules for . . PNEUMATICS . .11 



Press, Bramah's hydraulic explained ..... HYDROST.S. MEcn.i. 23 



Pressure of air, particular effects of PRELIMINARY TREAT. 19,26 



. . numerous experiments on .... PNEUMATICS . 13,21 



.. considered as a mechanical agent . . MECHANICS, t. i. . 24 



centre of ........ HYDROSTATICS . 11, 28 



equilibrium of . . . . . . . HYDRAULICS . . 2 



of fluids ........ HYDROSTATICS 2, 10, 11 



.. transmitted in all directions . . . PNEUMATICS . 5 



high and low, steam-engines, described ... MECHANICS, t. i. . 32 



of water, immense power of detailed . . . HYDROSTATICS . 7 



communicates double refraction to bodies . . . POLAR. OF LIGHT . 7 



its effects upon regular crystals .... . 56 



Primary colours of rays of light ...... OPTICS . . 23 



Principle, D'Alembert's, in mechanics .... MECHANICS, t. ii. . 2 



. . of virtual velocities, explained .... 2, 28, 42 



Prism, neat of the sun's rays when separated by a . . HEAT . . 29 



Prisms, refraction of light through . . . OPTICS . . 7 



Prismatic rays, comparative temperature of . . . . . . .29 



spectrum de-oxydizing and illuminating power of . . . 29 



physical properties of . . . . . . .28 



Proper position of sails in a windmill . . . . . MECHANICS, t. i. . 25 



velocity of water-wheels . . ". . . . HYDRAULICS . . 27 



nature of air . . . . . PNEUMATICS . 2 



of caloric ~ . . . . HEAT . 1 



.. of light ...... OPTICS . . 1 



Proportions, definite, or mathematical chemistry, concerning . PRELIMINARY TREAT. 15 



Pulley and rope, a mechanical instrument .... MECHANICS, t. ii. . 31 



Pulleys, fixed and moveable, their efficacy .... . 33 



systems of, described ...... . 34, 37 



White's pulley, double moveable, described . . . 35 



. . Spanish Burtons, described ..... . 3 



. . with oblique ropes ...... . 39 



Pulse-glass, principle of ....... HEAT . . 56 



Pump, air, described . . . ' . . . PNEUMATICS . . 14 



Pumps, air-vessel for ....... HYDRAUL. 13. PNEUM. 25 



calculations for the discharge of . ' . . . HYDRAULICS . . 16 

 of the power requisite to work . . HYDRAUL. 21. PNEUM. 22, 25 



Ctesebes and De la Hire's HYDRAULICS . . 15 



centrifugal . . . .*.. ' 19 



chain, and Vera's rope pump . . . ' . " . 



eccentric pump ....... . 16 



force pump ....... HYDRAUL. 11. PNEUM. 24 



lifting 10 23 



lift and force . . . ~ . . . 



suction pump . . . . . . . PNEU 



suction pipes for their action . . . . 



errors in the construction of 

 Pyrometer, general account of . . ' . . 



comparison of Wedgewood's with the scale of F' 

 heit's thermometer . ' , , 



