INDEX TO VOLUME 77. 



467 



MAXIMUM STRENGTH OP TUBE. 



i mperature agree with Siemcns's, 

 C. W., 14G) ; (formula of, of ratio 

 of increase of resistance with 

 temperature in pure metal, 146 ; 

 triiipcruture, high, not available 

 for, 147) ; investigations on con- 

 ductivity, 48, 78, 146. 



Maximum strength of tube, due to 

 determined proportion of diameter 

 and thickness, 133 ; to resist 

 strains at certain height above 

 ground, 133. 



Mayer and Auerbach, investigation 

 of Gramme's dynamo-electric 

 machine, 216. 



Measuring and regulating electric 

 currents, Siemens 's, C. W., machine 

 for, 201. 



Mechanical transmitter, 114. 



Mediterranean and Atlantic, differ- 

 ence of bottom of, 117. 



Mediterranean cables, destruction of 

 by marine insects, 118. 



Memory analogous to phonographic 

 record, 197. 



Mercury unit of resistance, 93. 



Merrifield, C. W., telegraph cable 

 ship Faraday, discussion of paper 

 by, 180183. 



Messages sent simultaneously in both 

 directions, 36. 



Metallic reflectors for electric 

 lighting, 234. 



Metallurgy, dynamo-electric current 

 applicable to, 220. 



Methods, various, of testing, 91. 



Microphone (action in, difference of 

 opinion regarding, 196 ; due to 

 variation of electrical resistance, 

 caused by vibration with variable 

 pressure, or lateral increase of 

 points of contact, 196) ; applicable 

 to physiological research, 197 ; 

 with crystalline selenium substi- 

 tuted for carbon affected power- 

 fully by light, 197. 



Miller, Professor, chemical investiga- 



OHM'S LAW. 



tion of Rangoon cable, 80 ; on 

 india-rubber, 105. 



Miller-Casella thermometer and 

 electrical thermometer, deep sea, 

 compared, 267. 



Moncel, Count du, discovered elec- 

 trical resistance of carbon to vary 

 inversely with pressure, 204. 



Montgomerie, exhibited gutta-percha 

 in 1844 at Society of Arts, 184. 



Morse, chemical electric telegraph, 

 1838, 18 ; instrument, Clark, L., 

 on use of, 41 ; and double-needle 

 instrument compared by Cla? - k, L., 

 41 ; (recording instrument, advan- 

 tages of, 33 ; consists of, 21). 



Movement of plants, Darwin on, 

 257. 



NEEDLE telegraph, inadmissible for 

 long lines, 45. 



New dynamo-electric machine, 

 Siemens's, C. W., less liable to 

 derangement, and may be driven 

 without variation of speed by 

 smaller engine, 219 ; steadier 

 light from, with greater average 

 economy of power, 219. 



Newall and Co., sheathing of iron 

 wire used for cables, 26 ; sub- 

 marine telegraph system of, 

 Highton, E., on, 41, 42. 



Niagara Falls, energy wasted at, 

 equivalent to 17 million horse- 

 power, or total coal production of 

 the world, 209. 



Northern latitudes, crops ripen 

 quickly in summer of, 230. 



OERSTED, electro-magnetism, dis- 

 covery of in 1821,18. 



Oersted and Ampere, and electro- 

 magnetism, Clark, L., on, 39. 



Ohm's law, 169 ; and underground 

 cables, 29. 



H H 2 



