ELECTRICITY. 



251 



strengths of current employed. Since, how- 

 ever, the increase of magnetism from the sec- 

 ond last to the last observation, in cobalt, was 

 much greater than in nickel, it is not impos- 

 M!>!I- tint, with very strong electric currents, 

 tin- iiKi^notisiii of cobalt may be greater than 

 thai of nickel. Unlike the nickel, the cobalt 

 pu-i-e was not without coercive force. 



New Electro- Motor. In a new electro- 

 motor recently exhibited in London by its 

 inventor, Chutaux, the primary force is sup- 

 plied by a battery of eight or more cells, 

 being a modification of the Bunsen battery. 

 The elements used are graphite and unamal- 

 gamati'd zinc, and the exciting fluids are sul- 

 phuric acid and bichromate of potash in the 

 inner (or graphite) cell, and a solution of acid 

 sulphate or bisulphate of potash in the outer 

 (zinc) cell. No material action is exerted on 

 the zinc while the battery is at rest, hence the 

 reason for dispensing with the process of amal- 

 gamation. Two or more horseshoe electro- 

 magnets, with their poles upward, are worked 

 by the current, a wheel rotating on an horizon- 

 tal axis immediately above and almost touch- 

 ing them. This wheel is practically.formed of 

 two parallel wheels joined at their circumfer- 

 ence by a series of soft-iron bars. As soon as 

 the current is set up the wheel begins to re- 

 volve, owing to the attraction between the 

 electro-magnets and the iron, the motion being 

 kept up, and rapidly increased, by means of a 

 simple automatic " current-re verser." The 

 principal feature to which the inventor draws 

 attention is the construction of the transverse 

 soft-iron bars, each of which is composed of 

 seven thin plates, much being thus gained in 

 intensity of magnetization, and consequently in 

 mechanical power. By a series of ingenious 

 devices the machine is applied to the working 

 of pumps, sewing-machines, lathes, etc., as a 

 substitute for manual or foot labor. It is not 

 of course in any way intended to supersede 

 steam, its object being the simple and easy 

 performance of labor of a light description. 

 The battery is free from smell, and, being very 

 u constant," will last for a long time without 

 renewal, the trouble involved in starting and 

 stopping the machine being practically nil. 



Influence of the Electric Current on the 

 Dimensions of Iron. The change in length of 

 a conductor, through which an electric current 

 is passing, has been measured by Exner, whose 

 method is free from the error caused by the 

 expansion due to the heat produced by the cur- 

 rent. In making this measurement, two pieces 

 of the same wire of nearly equal lengths were 

 hung one over the other, and so connected 

 with a battery that the current might be 

 passed through either. The lower wire was 

 passed through a glass which might be filled 

 with water if desired. The elongation was 

 measured by resting the end of the wire on a 

 lever carrying a mirror whose deflection was 

 read by a microscope and scale. The current 

 taing passed successively through the two 



wires, a different deflection was obtained in 

 each case, but these were rendered equal by 

 inserting an additional resistance in circuit 

 with that wire whose elongation was greater. 

 The tube was now filled with water BO as to 

 carry off the heat generated in the lower wire 

 as rapidly as possible. It was found that the 

 galvanic expansion was only 1.2 to 2.2 per 

 cent, of the heat-expansion ; and no connec- 

 tion was recognizable with the nature ot tho 

 metal employed. If it be considered that 

 these values, of course, can only be an upper 

 limit, it will follow, from the smallness of the 

 effect obtained, that there is no sufficient 

 ground for the hypothesis of a special expan- 

 sion power of the galvanic current. There 

 can hardly be any doubt that the slight expan- 

 sion which the water- inclosed wire still shows 

 is simply and alone due to the heat remaining 

 in it. 



Magnetic Equivalent of Heat. In Lamin 

 and Roger's decisive experiment establishing 

 the production of heat through disappearance 

 of magnetism, the soft iron of an electro-mag- 

 net was placed in the reservoir of a large ther- 

 mometer of oil of turpentine; on sending an 

 interrupted current through the spiral, it was 

 observed that the liquid expanded. The con- 

 clusion hence drawn was, that during each mag- 

 netization a part of the electricity goes into 

 the iron, producing magnetism, and that at the 

 moment of demagnetization this magnetism is 

 transformed into heat. In further investigat- 

 ing this subject, Cazin employed three different 

 methods of experimentation. In the first, the 

 iron core was inclosed in an hermetically-closed 

 vessel filled with petroleum, and surrounded by 

 the magnetizing spiral. From the vessel pro- 

 ceeded a capillary tube, also containing petro- 

 leum, and the changes of level in it were ob- 

 served when the core was magnetized by an in- 

 terrupted current. But inasmuch as change of 

 level might arise, not from heat-action, but 

 from the expansion of the iron by magnetism, 

 the following experiment was arranged : 



Into the vessel containing the liquid and the iron 

 core were introduced some closed glass tubes, which 

 displaced a third of the liquid ; the vessel was then 

 closed, and the experiment repeated. It' the expan- 

 sion of the iron were the cause of the change of level, 

 this must now be the same as in the experiment 

 without the glass tubes; if, on the other hand, the 

 change of the level were due to the beat produced, 

 it must now be different, for, instead of three volumes 

 of liquid, two volumes of liquid and one volume of 

 glass were heated by tlie same quantity of heat. 

 The experiment then revealed a difference, which 

 corresponded to the difference of the specific heats 

 and confinements of expansion of petroleum- oil and 

 glass. 



It was thus proved that the discontinuous 

 magnetization of an iron core produces heat. 



In another method for demonstrating and 

 measuring this heat-effect, the core was an 

 iron tube, closed at both ends with corks, and 

 inclosing the bulb of a common thermometer. 

 Here, again, there was heat-action when the 

 spiral was traversed by an interrupted cur- 



