August 24, 1S82] 



NATURE 



39: 



through their action. To avoid such interference the telephone 

 wires if suspended in the air require to be placed at some 

 distance from telegraphic line wires, and to be supported by 

 separate posts. Another way of neutralising interference consists 

 in twisting two separately insulated telephone wires together, so 

 as to form a strand, and in using the two conductors as a 

 metallic circuit to the exclusion of the earth ; the working 

 current will, in that case, receive equal and opposite inductive 

 influences, and will therefore remain unaffected by them. On 

 the other hand two insulated wires instead of one are required 

 for working one set of instruments ; and a serious increase in 

 the cost of installation is thus caused. To avoid this Mr. Jacob 

 has lately suggested a plan of combining pairs of such metallic 

 circuits again into separate working (airs, and these again with 

 other working pairs, whereby the total number of telephones 

 capable of being worked without interference is made to equal 

 the total number of single wires employed. The working of 

 telephones and telegraphs in metallic circuit has the further 

 advantage that mutual volta induction between the outgoing and 

 returning currents favours the transit, and neutralises on the 

 other hand the retarding influence caused by charge in under- 

 ground or submarine conductors. These conditions are particu- 

 larly favourable to underground line wires, which possess other 

 important advantages over the still prevailing overground system, 

 in that they are unaffected by atmospheric electricity, or by 

 snov-storms and heavy gales, which at not very rare intervals of 

 time put us back to pre-telegraphic days, when the letter-carrier 

 was our swiftest messenger. 



The underground system of telegraphs, first introduced into 

 Germany by Werner Siemens in the years 1847-8, had to yield 

 for a time to the overground system owing to technical difficulties, 

 but it has been again resorted to within the last four years, and 

 multiple land cables of solid construction now connect all the 

 important towns of that country. The first cost of such a 

 system is no doubt considerable (being about 38/. per kilometre 

 of conductor as against 8/. 10/. the cost of land lines) ; but as 

 the underground wires are exempt from frequent repairs and 

 renewals, and as they insure continuity of service, they are 

 decidedly the cheaper and better in the end. The experience 

 afforded by the early introduction of the underground system in 

 Germany, was not, however, without its beneficial results, as it 

 brought to light the phenomena of lateral induction, and of faults 

 in the insulating coating, matters which had to be understood 

 before submarine telegraphy could be attempted with any 

 reasonable prospect of success. 



Regarding the transmission of power to a distance the electric 

 current has now entered the lists in competition with compressed 

 air, the hydraulic accumulator, and the quick running rope as 

 used at Schaflfbausen to utilise the power of the Rhine fall. The 

 transformation of electrical into mechanical energy, can be 

 accomplished with no further loss than is due to such incidental 

 causes as friction and the heating of wires ; these in a properly 

 designed dynamo-electric machine do not exceed 10 per cent., 

 as shown by Dr. John Hopkinson, and, judging from recent 

 experiments of my own, a -till nearer approach to ultimate per- 

 fection is attainable. Adhering, however, to Dr. Hopkinson's 

 determination for safety's sake, and assuming the same per- 

 centage in reconverting the current into mechanical effect, a total 

 loss of 19 per cent, results. To this loss must be added that 

 through electrical resi-tance in the connecting line wires, which 

 depends upon their length and conductivity, and that due to 

 heating by friction of the working parts of the machine. Taking 

 these as being equal to the internal losses incurred in the double 

 process of conversion, there remains a useful effect of 100 — 

 38= 62 percent., attainable at a distance, which agrees with 

 experimental results, although in actual practice it would not be 

 safe at present to expect more than 50 per cent, of ultimate 

 useful effect, to allow for all mechanical lo-ses. 



In using compre-sed air or water for the transmission of power 

 the loss cannot be taken at less than 50 per cent., and as it 

 depends upon fluid resistance it increases with distance more 

 rapidly than in the case of electricity. Taking the loss of effect 

 in all cases as 50 per cent., electric transmission presents the 

 advantage that an insulated wire does the work of a pipe capable 

 of withstanding high internal pressure, which latter must be more 

 costly to put down and to maintain. A second metallic con- 

 ductor is required, however, to complete the electrical circuit, 

 as the conducting power of the earth alone is found unreliable 

 for passing quantity currents, owing to the effects of polariza- 

 tion ; but as tbis second conductor need not be insulated, water 



or gas pipes, railway metals or fencing wiie, may be called into 

 requisition for the purpose. The small space occupied by the 

 electro-motor, its high working speed, and the absence of waste 

 products, render it specially available for the general distribution 

 of power to cranes and light machinery of every description. 

 A loss of effect of 50 per cent, does not stand in the way of 

 such applications, for it must be remembered that a powerful 

 central engine of best construction produces motive power with 

 a consumption of two pounds of coal per horse-power per hour, 

 whereas small engines distributed over a district would consume 

 not less than five ; we thus see that there is an advantage in 

 favour of electric transmission as regards fuel, independently 

 of the saving of labour and other collateral benefits. 



To agriculture, electric transmission of power seems well 

 adapted for effecting the various operations of the farm and 

 fields from one centre. Having worked such a system myself in 

 combination with electric lighting and horticulture for upwards 

 of two years, 1 can speak with confidence of its economy, and 

 of the facility with which the work is accomplished in charge of 

 untrained persons. 



As regards the effect of the electric light upon vegetation there 

 is little to add to what was stated in my paper read before Section 

 A la-t year, and ordered to be printed with the Report, except 

 that in experimenting upon wheat, barley, oats, and other cereals 

 sown in the open air, there was a marked difference 'between the 

 growth of the plants influenced and those uninfluenced by the 

 electric light. This was not very apparent till towards the end 

 of February, when, w ith the first appearance of mild weather, 

 the plants under the influence of an electric lamp of 4,000 

 candle power placed about 5 metres above the surface, developed 

 with extreme rapidity, so that by the end of May they stood 

 4 feet high, with the ears in full bloom, when those not under 

 its influence were under 2 feet in height, and showed no sign of 

 the ear. 



In the electric railway first constructed by Dr. Werner Siemens, 

 at Berlin, in 1S79, electric energy was transmitted to the moving 

 carriage or train of carriages through the two rails upon which 

 it moved, these being sufficiently insulated from each other by 

 being placed upon w ell creosoted cross sleepers. At the Paris 

 Electrical Exhibition the current was conveyed through two 

 separate conductors making sliding or rolling contact with the 

 carriage, whereas in the electric raib< ay now in course of 

 construction in the north of Ireland (which when completed 

 w ill have a length of twelve miles) a separate conductor will be 

 provided by the side of the railway, and the return circuit 

 completed through the rails themselves, which in that case need 

 not be insulated ; sreondary batteries will be used to store the 

 surplus energy created in running downhill, to be restored in 

 ascending steep inclines, and for passing roadways where the 

 separate insulated conductor is not practicable. The electric 

 railway possesses great advantages over horse or steam-power 

 for towns, in tunnels, and in all cases where natural sources of 

 energy, such as waterfalls are available ; but it would not be 

 reasonable to suppose that it will in its present condition com- 

 pete with steam propulsion upon ordinary railways. The trans- 

 mission of power by means of electric conductors posse-ses the 

 further advantage over other means of transmission that, provided 

 the resistance of the rails be not very great, the power commu- 

 nicated to the locomotive reaches its maximum when the motion 

 is at its minimum — that is, in commencing to work, or when 

 encountering an exceptional resistance — whereas the utm> st 

 economy is produced in the normal condition of working when 

 the velocity of the power-absorbing nearly equals that of the 

 current-producing machine. 



The deposition of metals from their solutions is perhaps the 

 oldest of all useful applications of the electric current, but it is 

 only in very recent times that the dynamo current has been 

 practically applied to the refining of copper and other metals, 

 as now practised at Birmingham and elsewhere, and upon an 

 exceptionally large scale at Ocker, in Germany. The dynamo 

 machine there employed was exhibited at the Paris Electrical 

 Exhibition by Dr. Werner Siemens, its peculiar feature being 

 that the conductors upon the rotating armature consisted of solid 

 bars of copper 30 mm. square, in section, which were found 

 only just sufficient to transmit the large quantity of electricity of 

 low tension necessary for this operation. One such machine 

 consuming 4-horse power deposits about 300 kilogrammes of 

 copper per 24 hours ; the motive power at Ocker is derived 

 from a waterfall. 



Electric energy may also be employed for heating purposes, 



