MAGXETO-ELECTPJCITY. 



491 



'y at the time when the other current is at its 

 maximum, so that if now the inverted currents 

 can be again inverted in both of these distinct 

 currents, and that the two now flowing in one 

 direction can be united as one compound cur- 

 rent, it is evident that the result will be a cur- 

 rent nearly as uniform as that from a galvanic 

 battery, with the advantage of equable con- 

 tinuity. This is done by the two commutators, 

 which consist each of two insulated rings of 

 metal, of such a form at the periphery that 

 two rollers or rubbers change sides from one 

 disk to the other at the same instant that the 

 current is reversed. Then, by combining the 

 two commutators, a compound current is ob- 

 tained that will produce a constant white light 

 or perform any of the other functions of the 

 galvanic current, and in a more perfect man- 

 ner, as it is more uniform in its action. 



A steady and constant current thus obtained 

 from the magneto-electric machine is only one 

 part of the problem of producing a constant 

 and steady light, and, although the most im- 

 portant part, still it would be perfectly useless 

 without an efficient lamp or regulator. In or- 

 der to understand this 1 it is necessary to explain 

 that the carbon points used for producing the 

 light or for converting a portion of the electric 

 current into light, are consumed, and that the 

 rate of consumption is irregular, owing to the 

 irregularities in the structure of the substance 

 used, which is the kind of graphite deposited 

 in the gas retorts sawed up into pencils about 

 a quarter of an inch square ; but, as the con- 

 sumption is irregular, no clock-work with con- 

 tinuous motion could be employed for the pur- 

 fose of causing the carbons to approach as*" 

 consumed, for it must be understood that the 

 steadiness of the light as well as its brilliancy 

 depend on the two carbon points being main- 

 tained constantly at a certain distance corre- 

 sponding to the strength of the electric current. 



Many pieces of apparatus more or less com- 

 plicated have been invented from time to time 

 for the purpose of regulating the movements 

 of the carbon electrodes, but none of them, as 

 formerly constructed, could be used in a light- 

 house, because they were more or less uncer- 

 tain in their action, and because the clockwork 

 was too delicate and liable to accident in other 

 hands than those of an electrician. The ques- 

 tion, what constitutes a good regulator, must 

 be answered by stating what it must accom- 

 plish ; and moreover it must perform its sev- 

 eral functions in the most simple manner. It 

 must in the first place maintain the carbons at 

 a given distance, whatever be the variation in 

 the state of consumption, and must also be 

 capable of being adjusted to any strength of 

 current; secondly, if jy any accident the cur- 

 rent should be interrupted, and the light there- 

 by extinguished, the regulator should be ca- 

 pable of re-lighting at once with full brilliancy, 

 that is, not only must it allow the carbon 

 points to touch to reestablish the current, but 

 must separate them again instantly, or there 



would be no light. Such a regulator we have 

 here, for its construction is simple, and it per- 

 forms its different functions in a most perfect 

 manner. Its construction is this : The upper 

 carbon is attached by a kind of small vice to a 

 bracket, standing out from a tube, which slides 

 freely in a column. The lower carbon is fixed' 

 in the end of another tube, exactly under t ie 

 other carbon. Both of these tubes are put in 

 motion thus : Two cords, passing over pulleys, 

 properly arranged, are wound on one spindle, 

 but in opposite directions. On turning a stud 

 fixed on the end of the spindle the regulator is 

 wound up ; that is, the top bracket is raised 

 and the lower tube depressed. On removing 

 the hand from the stud, the upper tube would 

 descend, and, being loaded, would cause the 

 lower tube to rise ; but to prevent this, while 

 the regulator is out of use a bolt is pushed in, 

 which prevents any movement in the regulator 

 till it is again withdrawn. The regulator being 

 wound up, the carbons are firmly fixed in their 

 places by tightening the holders, and are then 

 adjusted so as to bring the points of the focal 

 plane by turning a spindle to which the fixed 

 end of the cord belonging to the lower carbon 

 is attached. So far the regulator is only a 

 means by which the carbons can mutually 

 approach each other with a certain relative 

 speed, depending on the different diameters of 

 the two parts of the spindle around which the 

 cords are wound. But if the carbon points 

 remain in contact, there will be no light. Some 

 contrivance, then, was necessary to separate 

 the points to the distance which, by expe- 

 rience, is found to give most light, and to main- 

 tain that distance between the points constant- 

 ly till the whole of the pair of carbons is con- 

 sumed. These two operations are accomplished 

 thus: The fixed end of the cord which works 

 the upper carbon is attached to one end of a 

 lever ; the other end of the lever has a piece of 

 soft iron attached to it, over an electric mag- 

 net, so that when the bolt is withdrawn, and 

 the carbons run together until they touch (thus 

 allowing the current to pass), this electro-magnet 

 instantly, by the action of the same current, 

 lifts the cord and with it the upper carbon, to 

 the required distance. But this is not all, for 

 the carbons would again run together were 

 there not some contrivance to prevent them. 

 To accomplish this, advantage is taken of these 

 two facts : first, that the quantity of electricity 

 is proportional inversely to the distance be- 

 tween the carbon points; secondly, that the 

 strength of an electro-magnet is proportional 

 to the quantity of electricity passing through 

 the wire that surrounds it. Bearing these two 

 facts in mind, it will be easy to understand the 

 use of the second electro-magnet. Over this 

 electro-magnet, at a small distance above it, is 

 placed a lever, one end of which is drawn down 

 by a spring, the strength of which can be regu- 

 lated by a thumb-screw. The fulcrum is be- 

 tween this end and the centre. The other end 

 of the lever is furnished with a catch and im- 



