EXHIBITION OF ELECTRICITY AT PARIS. 



255 



by the current preserves in the condition of 

 unstable equilibrium the energy which has been 

 expended in effecting it. The molecular ten- 

 sion is loosed, and the whole store of energy 

 is given back again in the form of an electric 

 current, when the two plates of the cell are 

 brought into metallic connection. The chemi- 

 cal work is then reconverted into electric en- 

 ergy, the peroxidized plate and the deoxidized 

 plate both returning into their former condi- 

 tion, and a voltaic current being evolved while 

 the active exercise of their chemical affinities 

 continues. 



Sir William Thomscn has designed an auto- 

 matic device by which, when a Faure battery 

 is connected with a dynamo which supplies the 

 current for a. circuit of electric lights, the sur- 

 plus electricity generated by the machine can 

 be taken up by the accumulator, the circuit 

 between them being made and broken auto- 

 matically. With this appliance the lamps can 

 be supplied from the battery with sufficient 

 light-giving power for some hours after the 

 machine has stopped. This would not only be 

 an economy, but would avert the extinction of 

 the lights which occurs when any accident be- 

 falls the machinery. The high-pressure gas- 

 motors of Otto have been of great service in 

 furnishing power economically for Gramme's 

 electro machines. By mingling illuminating 

 gas and air in proper proportions and under 

 pressure, a quiet combustion and regular expan- 

 sion are obtained, free from explosive shocks. 



The Siemens electrical railway, which has 

 been in use for some time in Berlin, was the 

 first practical application of electricity to loco- 

 motion. As in the similar device of Edison, 

 the electric current can be conveyed by the 

 iron rails ; but usually it is carried on a wire 

 which is tapped by carriers on the car, setting 

 in motion a dynamo-machine, which actuates 

 the wheels on one side of the car by a chain- 

 connection geared to their axles. The attempt 

 has been made in Paris with the Faure battery 

 to obviate the use of conducting wires, and en- 

 able a car to be propelled over any railway by 

 a dynamo fed with the electricity in the accu- 

 mulator until the stored-up energy is exhausted. 

 The electrical railway-car is a large tram-car. 

 The only feature observable in which it differs 

 from other cars is presented by the couple of 

 wires which travel with it and connect it by 

 running contact with two conductors suspend- 

 ed on posts like ordinary telegraph-wires. 

 The current generated by a stationary dyna- 

 mo-electric machine is thus introduced into 

 the locomotive and actuates an electro-mag- 

 netic machine under the floor, which drives 

 the wheels of the car. In the beginning the 

 rails were used as the conductors of electricity, 

 instead of suspended wires. That plan was 

 practiced on the elevated railway which was 

 built for the Siemens electric cars in Berlin. 



Tresca, a well-known electrician of Paris, 

 has experimented on the application of elec- 

 tricity to plowing. With a Gramme machine 



making 1,200 revolutions a minute, he plowed 

 a furrow 222 metres long with a double Brabant 

 plow at a velocity of 88 centimetres a second. 

 The effective work was about 3 horse-power. 

 The current was transmitted on copper wires 

 from the generator to two Gramme machines 

 which actuated windlasses. The plowing-ma- 

 chine invented by Menier is propelled by the 

 large form of Gramme dynamo-machine, and is 

 capable of doing the work of eighteen horses. 

 It consists of two electrical locomotives contain- 

 ing large coils of wire rope by which a triple- 

 shared reversible plow is drawn backward and 

 forward across a field. When a furrow has 

 been plowed, the electric machine is geared to 

 the heavy wheels of the locomotive, propelling 

 it forward to the next position ; and then the 

 plow is tilted over, bringing the three opposite 

 shares into action, and drawn across the field 

 in the reverse direction. 



An electric brake has been invented by a 

 French electrician, Achard. There are two 

 rings of iron on the axle of each pair of wheels, 

 and facing these two larger rings on an inde- 

 pendent axle, which are connected with a pow- 

 erful electro-magnet. The current is generated 

 by an electric machine in the locomotive. The 

 brake is kept from the wheels by strong spiral 

 springs, and the independent axle remains sta- 

 tionary until a current is generated. Then the 

 larger rings are converted into magnetic poles ; 

 the attraction of the rings on the wheel-axle 

 causes the magnetic rings to revolve and wind 

 up a chain connected by levers with the brake. 

 The pressure of the brake can be increased or 

 diminished by the engineer through an appli- 

 ance depending on the principle of variable re- 

 sistances. Many forms of small motors driven 

 by element batteries have been devised, and 

 the applications of these for sewing, embroid- 

 ering, and other light work, are often as prac- 

 tical as they are elegant. The most notable 

 of these contrivances are by French inventors. 

 They are of slight account, however, in com- 

 parison with the mechanical generation of elec- 

 tricity and its applications. An interesting use 

 of the Gramme machine was shown at Paris 

 in the rock-drill, which rotates under the in- 

 fluence of the dynamo while it is held to its 

 work by a head of water, which, in the Paris 

 water-works, affords a pressure of three at- 

 mospheres. 



One of the most important improvements in 

 telegraphy is the harmonic telegraph of Elisha 

 Gray, which has been for some time in opera- 

 tion between Boston and New York. A tun- 

 ing-fork of a certain pitch is kept vibrating 

 at the sending-station by an electric current, 

 which can be intermitted by the key of a 

 Morse instrument. Through the medium of 

 the tuning-fork the circuit of the telegraph- 

 wire is joined and broken at each vibration, 

 and at the receiving-station another tuning- 

 fork is acted upon by the intermittent current, 

 and vibrates at the same rate. When the op- 

 erator at the dispatching-station touches the 



