306 Index. 



Nitrous ether, how made, ii. 218 gas, nature and pro- 

 perties of, ii. 47. 



Nodes of the moon explained, i. 322, 323 their influence 

 on eclipses, ii. lg to 26. 



Non-conductors, what substances so called, i. 97. 



Non-electrics, what, i. 102. 



O. 



Objects and general principles of these lectures explained, 

 i. 1. 



Oblique ascension, defined, i. 267 sphere, why so called, 

 265 properties of the, ib. 



Octants of the moon, i. 314. 



Oils, chemical account of, considered as compound com- 

 bustible substances, ii. 21() to 223 animal, 28Q. 



Opaqueness and transparency, principles of, explained, i. 

 137 to 141. 



Opaque, what bodies so called, i. 137 to 1 r2. 



Optical glasses, principle of, i. 151 various forms of, 152 

 effects of, 153. 



Optics, amusing science of, i. 164 new discoveries in the 

 science of, 213. 



Ores of metals, ii. 238. 242. 



Oxides, comparative weight of, ii. 230. 



Oxidizement of metals, ii. 227 to 238. 



Oxygen, a simple substance in chemistry, ii. 36 chemi- 

 cal account of, 38. 44 the cause of acidity, 42 effect 

 of, on metals, 43. 



P. 



Pallas, particulars concerning the newly discovered planet, 



290, 291. 304 to 306. ^ 

 Pa pin's digester, description of the machine so called, ii. 



76. 



Paradox, the hydrostatic, i. 39. 

 Parallax, explanation of the diurnal and the annual, i. 



269 illustrations of the horizontal, 296. 303. 

 Parallel sphere, what so called, i. 264 appearance of the 



heavens to a, 264. 



