INDEX. 
Nitrate of copper, singular electro-mechanical phenomenon 
exhibited by, 188. 
Nitrogen, its effect on explosive mixtures of hydrogen and 
oxygen, 273. 
Nitrous oxide, ditto, ditto, 274. 
Nutation, lunar, determined by Dr. Brinkley, 77 — difference 
between values of, as determined by observations of the sun 
and stars, ib. 
Nuthatch caught in the Atlantic several hundred miles from 
land, 13. 
O 
Observatory at the Cape, Mr. Fallows’s choice of a site for, 457- 
temporary ditto, account of, and of the instruments 
in it, 458. 
Olejiant gas not acted on in mixture with oxygen by platina 
sponge at ordinary temperatures— effect of, in suspending the 
combination of gases by ditto, 275. 
Optic nerves , semi-decussation of, 222 — structure, 22 6. 
Ovaria of birds, their enlargement causes migration, 20 — of 
axolotl ; see axolotl. 
Owl seen in the midst of the Atlantic, 13. 
Oxide, carbonic ; vide carbonic oxide. 
Oxygen, absorbed by copper exposed to sea water in contact 
with atmospheric air, 153. 
mixtures of, with hydrogen and other gases, analysed 
by the platina sponge, 266 — 289- 
P 
Parallax, determination of its existence, and amount, by obser- 
vations of double stars again recommended, Part iii. 1. 
• of a Lyras, Dr. Brinkley on the, 471, et seq.- Re- 
marks on Mr. Pond’s observations on, 472. 
Pellicle of bismuth on mercury, its sudden motions when elec- 
trified, explained, 193, 195. 
Pendennis Castle , error of 4" in its longitude in the Trigonome- 
trical Survey detected, 360, et seq. 
Pendulum, conical — clocks with, used to determine velocity of 
sound, 427 — first made by Benzenberg, ib. 
Percussion, its effect in developing magnetism in iron and steel, 
197 — mode of applying it to produce the maximum effect, 
198. 
