INDEX. 
Hydrogen, effluvium of the supposed cause of certain electrical 
phenomena observed by M. Serrulas, 193 — explosive mixture 
of with oxygen, effect of platinum sponge on, 267 — ditto, diluted 
with hydrogen, 274. 
Hygrometer, Daniell’s, used in experiments on velocity of sound 
by Moll and Van Beek, 429 — and how. 
I 
Illumination of the field of a telescope, singular phsenomenon re- 
specting, Part iii. 15 — proper degree of, differs for different 
stars, ib. 
Imponderability of ethereal bodies called in question, 185. 
Impregnable, distribution of magnetism on board of the, 349. 
Index errors of micrometers require to be frequently taken, Part 
iii. 19. 
Insects, brains of, Sir E. Home on, 1, 5 — medulla spinalis of, 5 — 
drawings of, by Bauer, Plates I, II. 
Instruments, astronomical, description of the transit and circle used 
by Mr. Fallows, 458, 462 — description of the instruments used 
by Messrs. Herschel and South in their observations of double 
stars, Part iii, 4, 12. 
Integral, definite, theorem concerning one, 128. 
Iris, its apparent ellipticity not the cause of the apparent direction 
of the eyes in a portrait, 248. 
Iron, developement of magnetism in, by percussion, 197 — protects 
copper from sea- water, 155, 156 — is protected by zinc, 158 — its 
electro-mechanical properties in alloy with mercury, 183 — solid 
amalgam with mercury, 183, note. 
Iron, cast, forms the best protector for copper, 243. 
Ivory, James, A. M. F. R. S. on the figure of equilibrium of a re- 
volving fluid, 85. 
J 
Jenner, Edward, M. D. on the migration of birds, 12. 
Rev. G. C. a letter to Sir H. Davy, introducing the above 
paper, ] 1. 
K 
Knight, extraordinary power of his magnets, 221 — how perhaps 
produced, 221. 
Kooltjesberg, one of the stations chosen by Messrs. Moll and Van 
Beek for experiments on the velocity of sound, 429. 
