INDEX TO VOLUME II. 



455 



DARWIN. 



DARWIN'S opinion on plant life, 

 criticism of, 257. 



Davy, E., chemical electric telegraph, 

 1838, 18. 



Davy, Sir H., decomposed potash 

 with Wollaston battery in 1807, 

 222 ; produced electric arc in 

 1810, 198, 222. 



Daylight in winter twice as effective 

 as electric light in experiments 

 on horticulture, 228. 



Deduction from experiments on 

 water absorption by insulating 

 materials, 100. 



Deep-sea cables, floats objectionable 

 for, 27 ; must not be too heavy, 

 106. 



Deep-sea electrical thermometer, 

 C. W. Siemens's, 162, 265 ; de- 

 scription of, 266 ; determinations 

 of compared with Miller-Casella 

 thermometer, 267 ; gives tempera- 

 ture of water at moment of ob- 

 servation, 271 ; report of tests of, 

 267, 268, 269 ; tables of readings 

 of at various depths, 268, 269, 270 ; 

 tested by Captain Bartlett on 

 steamship " Blake," 267 ; Thom- 

 son's marine galvanometer used 

 with, 267, 



De Foy et Breguet Fils, telegraph 

 instruments of, 22. 



Depth of sea, indication of, by strain 

 on dynamometer in paying out 

 cable, 186. 



Destruction of Mediterranean cable 

 by marine insects, 117. 



Deville furnace, developed and ap- 

 plied by G. Matthey, 221. 



Deville and regenerative gas fur- 

 naces, difference between methods 

 of obtaining heat in, 221. 



Dewar, J., recent application of elec- 

 tric arc to chemical research, 

 222. 



Diagram of electric resistance of 

 platinum, 14.~> ; of law of increased 



DISSOCIATION. 



resistance with temperature, ex- 

 planation of, 148 ; produced by 

 electric current measurer, 206. 



Dial instruments, Henley's and 

 Stcehrer's, 23 ; new with dead 

 beat ratchet motion, 45 ; Sie- 

 mens's, W., 23 ; Wheatstone's, 

 21. See A. B. C. 



Differential galvanometer, 121, 

 122. 



Differential measurement, theory of, 

 169. 



Differential Voltameter, acid em- 

 ployed of uniform strength,! 73; ac- 

 curacy of,175 ; applicable on board 

 ship,l 77; atmospheric pressure does 

 not affect reading of, 174; (battery 

 power, minimum for, 174 ; pro- 

 portional to resistance of, 174 ;) 

 calculation of tables used with, 

 method of, 175 177 ; calibration 

 of each voltameter tube separately, 

 175 ; currents, reversal of, 173 ; 

 description of , 170 ; electrical pyro- 

 meter and, connected, q. v.; india- 

 rubber pads covered with paraffin, 

 174 ; leakage of gas to be avoided 

 in. 176; moveable voltameter tubes 

 of, 170 ; platinized electrodes of, 

 170 ; portable, easily used, and 

 cheap, 177 ; precautions necessary 

 in using. 173 ; reservoirs moveable, 

 advantages of having, 174 ; resist- 

 ance measured in work done, 177 ; 

 simplicity of construction of, 177 ; 

 voltameter tubes, size of, how 

 affected, 175 ; and Wheatstone 

 diagram, tables of comparison of, 

 178, 179. 



Dioptric arrangements large and 

 small, 207. 



Discharge of cable, 32. 



Dissociation, temperature of com- 

 plete, limits temperature of com- 

 bustion, 221 ; temperature of 

 according to Ste. Claire Deville 

 and Bunsen, 221 ; temperature, 



