A/A' WILLIAM SIEMENS, F.R .V. 25 



iiy mechanical agency, on separating a permanent magnet from its 

 armature or surrounding coils, or by means of a voltaic quantity 

 liattcry and primary coils ; and are, in botli instances, by far the 

 chcajHiSt and least variable description of electric currents. The 

 reason why, since the discovery of magneto-electricity in 18:11, it 

 has again and again been abandoned in favour of battery currents, 

 may be traced to the imperfect means hitherto known or adopted 

 for its generation or suitable application ; but I hope to prove 

 hereafter that it can be employed at present with perfect success. 



Regarding the electric conductor or line-wire, this is either 

 suspended upon poles in the open air, or it is imbedded in gutta- 

 percha, and interred or submerged. Suspended line-wire generally 

 consists of galvanised or painted iron, of from one-eighth to one- 

 fifth of an inch in diameter, and supported, at intervals of from 

 60 to GO yards, from posts by means of insulators. The con- 

 struction of a really efficient insulator lias for many years occupied 

 the serious attention of electrical engineers, for upon it chiefly 

 depends the permanent efficiency of the line. A great variety 

 of insulators have been tried, some of which I am enabled, 

 by the kindness of the Electric Telegraph Company, to present 

 to the meeting. According to continental experience, the in- 

 sulator of Siemens and Halske has been found to combine the 

 desiderata of strength and insulating property in the highest 

 degree. It consists of a cast-iron bracket, assuming the form of 

 an inverted bell, with a cylindrical recess at the bottom. A 

 capsule of porcelain is firmly cemented, by means of sulphur mixed 

 with caput mortuum, into the recess, and into this again a stalk 

 of iron is cemented, which forming a peculiar twisted loop at the 

 end, supports and secures the line-wire. The insulating property 

 depends upon the dryness of an apron-like extension of the 

 porcelain capsule, which, under the protection of the cast-iron bell, 

 is not affected by either rain or dew. Every tenth support is a 

 stretching-post insulator, at which the line-wire is not only 

 supported but held firmly by means of cla\vs, an arrangement 

 which has been found very convenient during the erection of the 

 line-wire, and in case of repairs. An idea of the importance of a 

 good insulator may be formed from the fact, that the cost of 

 finding and repairing a single defect of the line-wire, in a country 

 like Russia, amounts on the average to 30. 



