308 Index. 



67 the air proved to be elastic, 6$ invention and ex- 

 planation of the air-pump, ib. experiments with this 

 instrument to show the mechanical properties of air; 

 its weight and pressure, 71> 72 its elasticity and com- 

 pressibility, 74. 



Polar inhabitants, appearance of the sun to the, i. 264. 



Polarization, a newly discovered properly of light, so 

 called, \.213 fixed and moveable, 214. 



Poles, definition of ihe, i. 263. 



Posture-masters and rope-dancers, how balance them- 

 selves, i. 229. 



Potass, its nature and qualities, ii. 54. 142 to 144. 



Potter's kiln, form of the, ii. 122. 



Precipitate, a, what so called in chemistry, ii. 34. 



Precession of the equinoxes, explained, i. 275. 



Press, a, constructed on the principle of the hydrostatic 

 bellows, i. 41. 



Prince Rupert's drops, ii. 105. 



Prism, nature and power of the, i. 147 Newton's ex- 

 periments with this instrument, to analyse light, 201, 

 202. 



Projectile force, nature of the, explained, i. 225, 226. 



Prussic acid, its nature and properties, ii. 166. 



Ptolomean system of the universe, i. 253. 



Pulley, principles of this instrument, and its mode of 

 acting, i. 23g. 



Pump, principles of the common, i. 53 of the forcing- 

 pump, and examples of it, 57, 5Q of the air-pump, 



Pyrites, ii. 205. 



R. 



Rain, phenomenon of, explained, i. 4. Q4 how predicted 

 by the barometer, Q3. 



Rainbow, phenomena of, explained, i. 5. 207. 



Rays of light, and their different kinds explained, i. 143, 

 144. 



Re-action, nature of the law of, explained, i. 227, 228 

 pretty experiment. illustrating, 228. 



Rectification of spirits, process of, ii. 211. 



Reflection (or reflexibility) of light, phenomena of, i. 2 

 lecture on, 142. 16'4 principle of reflection, 164 dif- 

 ferent kinds of mirrors, and their modes of action, 165 

 to 177- 



