176 Proceedings, &a, for 1885. 



series-multiple, but the total quantity is considerably less than 

 would be required in parallel series. 



The greatest objection seems to be the difficulty of attending 

 to the management of two or more dynamos in parallel series. 



There is another method in use, which is closely connected with 

 the above systems, though hardly deserving the name of separate 

 systems. It is known as the high resistance system. It has been 

 attempted to get greater efficiency by increasing the resistance of 

 the lamp, so that it may have a high ratio compared with that of 

 the dynamo and line. Probably the highest resistance is attained 

 in the Edison lamp, a hundred volt lamp. The limit to resistance 

 is the difficulty of manufacture, and the fact that the filaments are 

 not very durable under current. 



Secondary Systems. — In all the foregoing the actual current 

 generated by the djnamo is utilised in heating the lamp. But in 

 the secondary systems the main current is not so employed, but 

 passes into more mechanism, which, in its turn, supplies the lamps 

 with current. 



The principal of these are the motor and the secondary generator 

 systems. The secondary mechanism employed in the latter is 

 similar to the Rhumkorff induction coil. The most convenient form 

 of current conveying the requisite amount of energy is trans- 

 mitted through the mains, and passes into the secondary generator 

 as a primary circuit, and the secondary current is modified 

 to the purpose required by the winding or joining up of the 

 secondary wire. The main current is of high E.M.F. to avoid 

 heavy conductors, and must be of the " alternating current" class. 



This system has all the disadvantages of the series system in 

 danger and difficulty of control ; but as it has only to pass into the 

 secondary generator, and not into the dwelling-houses, the danger 

 is to a great extent obviated, and all the controlling required is 

 done in the secondary circuit. 



But besides these two we have another very important branch, 

 which, though it can hardly be classed as a separate system, yet 

 may be so important a factor in any other system as to give it a 

 distinctive name. This is the secondary battery. In this method 

 the electrical energy carried by the current, instead of passing 

 directly into the lamps, is sent through a suitable arrangement, and, 

 instead of being reproduced as heat, the energy is expended in 

 altering the molecular condition of the plates and liquids in the 

 battery, so as to form a store of chemical potential energy, which 

 can be for a time retained in that form, and subsequently, by 

 completing the circuit, be allowed to flow out in any form of 

 current that may be desired. Thus a high-tension current may le 

 employed for charging a secondary battery at a distance, and the 

 battery may afterwards be used to supply current to a set of lamps 

 in parallel series. 



