488 



PHYSICAL SCIENCES. 



CYANITE. 



Cyanite, changes effected in, by mag- 

 netism, 349. 

 Cyanotypes, coloured photographs 



obtained by, 206. 

 Cygni 61, distance from the sun of, 



389 ; orbit and mass of, 398, 399 ; 



colours, 401 ; mass, 404 ; proper 



motion, 405. 

 Cygnus, portion of the Milky Way 



lying between a Centauri and, 386. 

 Cylinders, rotating by electricity, 



313 ; electro-dynamic, 316. 



DALCOATH copper-mine, its tempera- 

 ture, 228. 



Daguerre, M., his inventions in pho- 

 tography, 205 ; action of light on 

 the iodide of silver explained by, 219. 



Daguerreotype, the, invention of, 205. 



Dalton, Dr., law of definite proportion 

 established by, 111 ; law of the 

 wind's rotation observed by, 125. 



Damoiseau, M., perturbations of a 

 comet computed by, 367. 



Daniell, Professor, Voltaic battery im- 

 proved by, 299. 



Daubuisson, M., observations of, in 

 mines, 228. 



Davy, Sir Humphry, his first attempts 

 to produce photographic pictures, 

 203-204 ; experiment of, proving 

 identity of heat and motion, 275 ; 

 experiments on the electric spec- 

 trum, 289 ; alkalies, earths decom- 

 posed by, 307. 



Days, law determining the length of, 

 71 ; period of the mean sidereal 

 and solar, 83 ; varying with the 

 seasons, 84 ; decimal division of, 

 84 ; seven, the most permanent 

 division of time, 85. 



Deccan, the, wheat ripening in, 250. 



December, 1832, disappearance of 

 Snturn's rings in, 67 ; coincidence 

 of mean and apparent time in, 84 ; 

 date of Christ's nativity, 85 ; the 

 astronomical year beginning in, 86. 



Decimal division of time, 84. 



Declinations of the moon, 97. 



Decomposition, effected by electricity, 

 307-308 ; by magnetism, 323 ; by 

 thermo-electricity, 333. 



DOLDRUMS. 



Delambre, his computations of the 

 length of the year, 359. 



Delta Cephei, a variable star, 391. 



Denmark, course of the tidal wave to, 

 94. 



Density , variable, impeding sound, 135, 

 136 ; of media, modifying refrac- 

 tion, 153. 



Densities of heavenly bodies, formula 

 finding, 56 ; experiments, 57, 58 ; 

 comparative of the terrestrial globe, 

 77, 78. 



Deserts, causing monsoons, 124; in- 

 fluence of, on temperature, 243. 



Dew, cause of its deposition, 269. 



Dialectics in electricity, 286. 



Diamagnetic substances, 335, 336. 



Diamagnetism defined, 335 : sub- 

 stances it is resident in, 336 ; dis- 

 covery, characteristics of, 347 ; 

 neutral substances obtained by pro- 

 portionate combination of, with 

 paramagnetism, ib. ; polarity of, 

 348 ; connected with arrangement 

 of molecules, 350-351 ; affected by 

 division r.nd compression, 351 ; pos- 

 sibly identical with paramagnetism, 

 356, 357. 



Diameter of the earth, 21 ; Jupiter's 

 polar, 27 ; excess of his equatorial, 

 39 ; apparent, of the sun and moon, 

 nearly equal, 40 ; of the earth,, 

 49; of bodies composing the solar* 

 system, 56 ; of Neptune, 63 ;. 

 comets lacking a sensible, 373 ; 

 contraction of, in comets, 377 ; 

 causes assigned for, 377, 378. 



of an annular nebula, 410 ; 



sensible, of a planetary nebula, 412, 



Diamond, the, polarized light reflected 

 from, 193. 



Dieppe, seen from Hastings, 157. 



Differential telescope, the, experi- 

 ments to be made by, 227. 



Discord, a, in music, 142. 



Diurnal tides of the atmosphere, their 

 duration, 121. 



variations in mean values of the 



magnetic elements, 343. 



Doebereiner, M., spontaneous combus- 

 tion discovered by, 112. 



Doldrums, region of the, 123. 



