50 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



LFEBBOJnV, 



has a socket for receivinfr and lioldiii^ the lower electrode 

 M, at its iii)i)er eiul ; ami this socket is furnished with set 

 screws for seciiriiii; the electrode in an ii))rif;ht position in 

 its centre, even thoufjjh that electrode should hajipen to be 

 of smaller size than the socket. At the bottom the socket 

 is made of a conical form, in order to kee]i the lower end 

 of the electrode steady and concentric, so that it may be 

 properly adjusted by the set screws, (/(/. Tliis shaft O has 

 a smootli straiffht part, below its socket, for a lenffth equal 

 to the distance between the apices of the fixed cones, C 

 and 1), which is equal to the amount of rise wliich the 

 shaft admits of, to compensate for tlie wear or shorteuing 

 of one of the electi'odes, while the li^iht is in action; this 

 smootli part of the shaft nio\ iiifi- freely thrcuiffh tlie hole 

 in the apex of the u])per cone. Below this smooth part 

 the shaft is continued for an equal lenffth, screwed ; the 

 threads of the screw {jivinar about one-twelfth of an inch 

 of rise for every turn. This screwed part works through 

 a nut c, which is set tijfht in tlie apex of the under cone 

 D, and passes dow n the centre of a hollow cylinder or 

 tube P, w hich is slotted internally (as shown at././' in figs. 

 '2 and '.i). A little cross piece of metal, Q, is set tight on 

 the bottom of the shaft (), by being screwed fast into its 

 end, and tliis cross-piece Q (which is afterwards more par- 

 ticularly ilescribed) fits across the tube P, taking into the 

 slots or grooves on each side, so that it can slide up or 

 down in them. Allien, therefore, the tube P is made to 

 revolve, it carries the shaft O round with it, by means of 

 the sliding cross-jiiece (}, and makes it to rise or sink by 

 its screw working in the fixed nut p, so that the shaft C), 

 carrying the electrode M in its socket, has a rotary motion 

 combined with its vertical motion, for the purpose of 

 equalizing the wear of the electrodes on all sides. The 

 tube P turns on a pivot //, which works in the bottom of a 

 circular box of metal H, which is screwed into a hole of 

 sufficient size in tlie bottom of the brass-plate G, which is 

 fixed to tlie upper surface of the wooden basement B. 

 The touching surfaces at the pivot;/ are coated with sil- 

 ver, as tliat metal jiresents a surface peculiarly fitted for 

 receiving the current of electricity. The upper end of 

 the tube P receives the outer p,art of the fixed nut e, on 

 which the tube turns, and is steadied as on an axis. On 

 the ujiper part of the tulie P, a worm-wheel S, carrying 

 forty teeth, is attached, which is made to revolve by a 

 horizontal double-thread tangent-screw T, the pitch radius 

 of which is one-tenth of an inch. To one end of the 

 screw is attached a crown-wheel U, carrying forty teeth, 

 which is actuated by pinions V and W, on an upright spin- 

 dle X. The pinions are at a somewhat greater distance 

 apart than the diameter of the crown-wheel U, and gear 

 into it from opposite sides, so that when the spindle X is 

 raised a little, tlie lower pinion V (having eight teeth), is 

 into the lower side of the crown-wheel ; but when the spindle is 

 sunk, the lower pinion is thrown out of gear, and the upper pinion 

 W gears into the u])per side of the crown-wheel ; and the spindle 

 continuing to revolve in the same direction as before, imparts a 

 reversed rotation to the crown-wheel. When the spindle is kept 

 at a medium degree of elevation, neither of tlie pinions is in gear 

 with the crown-wheel, so that it remains quiescent. This spindle 

 X is kept in its position by working through a hole in the middle 

 plate, F, of the apparatus, which plate is attached firmly to three 

 of the pillars c. The upper end of the spindle works through a 

 hole in the centre of the bottom of a circular brass box I, which is 

 fixed to the side of the under cone D, or to the under side of the 

 main-plate A. The box I contains a centrifugal regulator Y, which 

 consists of a bit of watch-spring bent into the form of the letter S, 

 carrying two little weights /; h at its ends, and fixed horizontally 

 across the top of the spindle by the middle part of the spring, 

 which fits into a cleft in the to]) of the spindle, and is secured by a 

 small nut. When the spindle is made to revolve too fast, the 

 weights at the end of the spring fly outwards by their centrifugal 

 force, and begin to touch and rul> against the sides of the circular 

 box I, which friction checks the motion. This description of go- 

 vernor ))reserves the motion more uniformly than the ordinary sort 

 of fly, which acts by the resistance of tlie air. Just below this 

 centrifugal governor there is a cross-piece ), inserted through a 

 transverse hole in the spindle X, so that when the spindle is at its 

 medium degree of elevation, that is to say, when its two pinions V 

 and W are neither of tliem in gear with the crown-wheel, the ends 

 of the cross-piece i meet a stop /c, which may project from any fixed 

 part of the apparatus, such as the cone D, and so stop the revolu- 



geared 



tions of the spindle ; while, as soon as the spindle is raised or low. 

 ered, the cross-piece i no longer meets the stop k, but passes over 

 or under it, amd allows the spindle to commence its revolutions 

 just before one of the pinions gears into the crown-wheel. The 

 spindle X is actuated and kept with a constant tendency to revolve 

 in one direction by a toothed wheel Z, keyed on to it just below the 

 middle plate F, and this wheel is driven by a train of wheelwork 

 W', supported lietween the middle and bottom plates F and G, 

 similar to ordinary clockwork, and which is driven by a spring in a 

 barrel /, acting on a fusee vi, driven by a cord or chain ; or the 

 wheelwork may have any other contrivance as its prime mover, as, 

 for instance, a common barrel with a cord and weight. The wheel 

 Z is of such thickness that the motion up and down, which the 

 spindle X admits of, will not ungear it from the next wheel in the 

 driving train. 



The mode in which the spindle X and its pinions are raised or 

 lowered, so as to vary the motion of the crown-w heel U, and thereby 

 of the electrode M, according to the exigencies ot the light, is as 

 follows: — The bottom of the spindle X terminates just below the 

 driving-wheel Z, and rests on a plate of ivory ji, which is supported 

 on a short upright stem of brass o, w hich has its lower end screwed 

 into a hole in the top of a solid cylinder of soft iron, p. This iron 

 can move freely up and down in the central hole of a reel ij, round 

 which a quantity of insulated copper wire is wound: one end of 

 this wire is led to the binding screw B, as before mentioned, w hich 

 connects it with the ])ositi\e wire of the galvanic regenerators, 

 and the other end to the wire which passes through the binding 

 screws L. The reel q of the regulator is fixed firmly to the wooden 

 basement B, and a cap r of soft iron fits over it ; but the iron of 

 the cap does not extend quite to the centre of the hole in it 



