INDEX. 
Perforations in fossil shells, mark the epoch of their deposition, 
415. 
Perkins, his process for multiplying fac-similes of copper- 
plates, 252. 
Piazzi, his Palermo Catalogue adduced to disprove southing of 
stars, 53. 
Pigeons , daily flight of, from the Hague to the Norfolk coast, 
and return, 13. 
Pile, voltaic ; vide poles. 
Placenta of seal, its structure and peculiarities, 237. 
Planets , figure of, 143 — its theory, 146 — only approximate as 
delivered by Legendre and Laplace, 150 — one condition of 
equilibrium neglected in, 150. 
Platina or platinum finely divided; its action on gaseous mix- 
tures, and application to their analysis, 266— sponge, how 
made and used, 268— balls of clay and, ibid. — wire of, its 
effect in producing slow combustion of mixed gases, 265. 
Pneumato-t borax , further particulars of a case of, 257. 
Polarity , not the natural condition of iron, 215 — acquired and 
lost almost instantaneously by soft iron, less so by soft steel, 
very slowly by hard, 216. 
Polar distances , north, of principal fixed stars— Dr. Brinkley’s 
remarks on, 50. 
Poles, of the voltaic pile, effects of on mercury under conduct- 
ing liquids, 173, 186 — appear to attract and repel globules of 
mercury, and why, 1 64, 167. 
Pond, J. Esq. examination of his reasoning respecting parallax 
of a Lyrae examined, 475, et seq. 
Portrait, Dr. Wollaston, on apparent direction of eyes in a, 
247 — why they look at the spectator in all directions, 254. 
Potassium, effect of, in changing the electro-mechanical rela- 
tions of mercury, 180 — sensible when only a millioneth part 
of it, 180. 
Preservation of anatomical specimens by brine, 234 — of cutting 
instruments by zinc cases, 249 — of copper, iron, &c. by nega- 
tive electricity, 151, 158 —of copper sheathing of ships, 151, 
242. 
Processes, simple and compound, for developing magnetism by 
percussion, 200. 
Proper motions of stars, verification of, iii. 21. 
Protectors, metallic, applied to copper immersed in sea water, 
243 — cast iron best fitted for, ibid. 
