1848."] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



51 



(througli wliich the brass stem n passes), tlie central part of the 

 top of the cap being' of brass soldered to the iron, of one-half of 

 the diameter of the iron cap itself. The action of the electricity 

 in tlie coil of the regulator 11 causes the iron centre p to rise or 

 fall, according to the quantity of electricity passing, and in so 

 doing, the spindle X, which rests on it, to rise or fall with it. 

 There is a little eye attached to tlie bottom of the iron centre, to 

 which is suspended a co>interpoise F' (an assortment of such coun- 

 terpoises being kept for use), of such weight as to allow the iron 

 centre to be just in equilibrium, or just ready to rise, when the 

 distance between the electrodes is such as to allow the electric cur- 

 rent to flow freely enough to produce a steady and certain light. 

 There is also a little ledge .«, around the lower end of the iron 

 centre, on which rests a disc t, of brass, of about the size indicated 

 in the drawing, fig. 2; which (when tlie iron centre falls below the 

 neutral point) becomes supported around its outer edge by a circle 

 of brass u, and is left behind on it, when the iron centre continues 

 to descend, thus relieving it of its weight ; while on the other 

 hand, if the iron centre is disposed to rise above the neutial point, 

 it has to lift the whole weight of the brass disc t. This arrange- 

 ment gives the iron centre a tendency to remain stationary at the 

 neutral point, which is that point at which the elevation of the 

 spindle X enables the cross-arm i to come into contact with the 

 stop A', and arrest the rotation, and so prevent unnecessary work- 

 ing of the machinery, until the electric current has varied so much 

 as to render desirable an adjustment of the distance between the 

 electrodes ; which the iron centre effects, as before described, by 

 rising or falling. 



The neutral position at which the iron centre p should rest, is 

 when the top of the iron centre is as far below the top of the regu- 

 lator reel as is represented in fig. 2. 



The brass ring u, which supports the equilibrium weight, that is 

 the brass disc t, is secured at the proper height by being attached 

 to a suflSciently stiff strip of brass ir, of a certain length, and which 

 is fixed by its other end to the other side of the wooden basement 

 B. The brass ring u can be adjusted to the requisite height e.\- 

 actlv, after the apparatus is made, by a niilled-headed screw pass- 

 ing thi'oiigh the wooden basement, and screwing down on the sup- 

 ])orting brass strip (not far from u), so as to depress it to the right 

 position. 



The sliding- cross-piece Q, before adverted to, is constructed in 

 the manner separately represented in fig. 4. A spring Q (of thin 

 hard brass, for instance,) is attached to one side of the cross part 

 by a small screw, so that when the cross-piece is placed in the slots 

 of the tube P, the spring always remains in close though not forci- 

 ble contact against the sides of the slots, so as to insure a good 

 conductitm to the electric current which has to tra\'erse the shaft, 

 aiul enter from the cross-piece into the slotted tube. 



The tangent-screw T is made not quite horizontal, hut inclined 

 at an angle of one in twenty, because the lower pinion V is smaller 

 than the upper one ; and therefore it is necessary that the lower 

 edge of the crown-wheel U should be tilted nearer to the axis of 

 the spindle X. The lower pinion is made smaller, in order that it 

 may the better wind down the main shaft O, after it has screwed 

 itself up, until the ends of the electrodes come into firm contact, 

 le^t it should stick in that position. 



The screw No. 1, which fastens the stand 3 of the tangent- 

 screw to the middle plate F, passes through a hole 4, enlarged side- 

 ways in the stand ; so that by only loosening the screw 1, the stand 

 may turn on the other screw 2, as a centre, so as to allow of the 

 tangent-screw T being adjusted to the right distance from the 

 centre of the wheel S, in order that it may work properly into its 

 teeth, or, \i hen required, to throw the tangent-screw out of gear 

 with it altogether. 



The thread of the screw of the main shaft O, should be of a 

 square form, so that it shall work with as little friction as may be, 

 when supporting the weight of the shaft and electrode. 



A cone of white glass or porcelain, E', is made to slip over the 

 upper cone C of the main plate, and is turned up at the edges (as 

 shown in figs. 1 and 2), to reflect the light better, and to catch any 

 dust and ash which may be thrown off from the electrodes. 



A glass shade, which may be ground partially or not, as desired, 

 fits oier the electrodes, M and N, and the stand K, and is screwed 

 down to the main-plate A, by the brass circle E, into whicli its 

 lower edge is cemented, whereby the electrodes are enclosed en- 

 tirely from the outer air. As soon as they have exhausted the 

 oxygen which is within the glass shade, they are no longer so rapidly 

 consumed. When the electrodes, however, are composed of some 

 inferior sorts of carbonaceous preparations they give light more 

 steadily if a very small quantity of atmospheric air is continually 

 allowed to enter; that is to say, just sufficient to burn away the 



I button of carbon which sometimes forms on the end of that elec- 

 trode which is not undergoing decomposition by the electric cur- 

 rent. \V^hen there are no holes in the glass shade to admit of a 

 small quantity of atmospheric air, two light valves may be inserted 

 in the main plate A, one opening inwards and the other outwards, 

 which would provide for the varying pressure of the air when the 

 temperature is altered by the presence or absence of the light 

 within. 



The coil of insulated wire of the regulator R, should be composed 

 of wire of such thickness as to conduct the electric current quite 

 freely. For an apparatus of the size represented in the engravings 

 it may be about three-sixteenths of an inch in diameter ; but if 

 electrodes of a larger size are employed, the wire should be pro- 

 portionally increased in thickness, and the regulator R, made as 

 large as the dimensions of the apparatus will admit of, in order 

 that the reel should take a sufficient number of turns of the thick 

 wire ; for with wires too thin, considerable heat is evolved from 

 them when transmitting the current. Two circular brass weights, 

 an, fitone over the other around the iv(u-y top »», which carries the 

 pivot of the spindle X ; their use is to enable an easier and more 

 precise adjustment of the weight on the iron centre than can be 

 effected by altering the large weight F', which is hung at the bot- 

 tom of the iron centre. 



When it is intended to use small currents of electricity, the 

 spindle X, and all its appurtenances, should be made very light, 

 and the iron centre may for the same object be made hoUow with 

 advantage ; its sides, however, should Jiot be less than one-twelfth 

 of an inch in thickness. , 



The electric current may be obtained from a galvanic apparatus 

 of any of the known sorts, or from any other convenient source; 

 and it may be used of various intensities and quantities. A good 

 degree of intensity to use, is such as would be afforded by one 

 hundred cells in a series of the usual sort employed in galvanic 

 apparatuses ; and the quantity of the current may vary from that 

 evolved by the consumption of less than one-and-a-half grains of 

 zinc per minute in each cell, to that evolved by the consumption of 

 more than fifteen grains of zinc per minute. 



The wire from the positive, that is, the zinc pole of the gah-anic 

 apparatus, is clamped with the binding screw at B-, which serves 

 as the conductor through the regulator coil, and then up to the 

 upper electrode N. The wire from the other, or negative pole of 

 the galvanic apparatus, is to be clamped with the other binding 

 screw at B-', whicli is connected by a slip of metal (copper) to the 

 bottom plate G of the apparatus, so that the current passing from 

 the lower end of the upper electrode N to the top of the lower 

 electrode M, then traverses the central shaft O, passes through the 

 cross piece Q, at its lower end, into the slotted tube P, and thence 

 through its pivot at bottom into the metallic box or cavity H, 

 which being in metallic connection with the bottom plate G, leads 

 the current to that plate and thence by the slip of co])per to the 

 other clamp, from which it passes in return circuit through the 

 negative wire of the galvanic apparatus. The current, when first 

 applied with the electrodes in contact, flows freely, and that causes 

 the regulator (being properly weighted) to raise the spindle X, and 

 thus put the apparatus into gear for screwing the centre shaft O 

 downwards, and gradually separating the electrodes, whereupon 

 the light begins to appear between them. 



The patentee then describes the method of preparing the carbon 

 for his electrodes : — About equal quantities are taken of coal of a 

 medium quality, and of the prepared coke, known as " Church's 

 Patent Coke," and both reduced to a state of fine powder and inti- 

 mately mixed together. The mixture is then placed in close 

 wrought-iron moulds, which may be made either to give the mix- 

 ture the form of a block, to be afterwards cut into pieces of the re- 

 quired shape, or to give at once to the mixture the form of the in- 

 tended electrode. In all cases it preferred to make the moulded 

 mass of not more than 3 or 4 inches in its least diameter, for when 

 larger it is liable to have fissures, and not to be of such uniform 

 density. The mixture being placed in these moulds, is subjected 

 to heat and heavy pressure until it becomes consolidated into a 

 very dense and firm mass. And when the mass is in a heated state 

 it is plunged into sugar, melted by beat (without the aid of any 

 liquid,) and kept therein for a short period. It is then taken out 

 and allowed to become cold, when it is placed amongst pieces of 

 charcoal in a close vessel, which is gradually heated until it attains 

 a full red heat, after which the temperature is increased to an in- 

 tense white heat ; at which it should be kept for many hours, or 

 even two or three days, according to the hardness and compactness 

 desired. Or the mass may be a second time immersed in the melted 

 sugar while hot, and the remainder of the process be again repeated 

 as before. 



8* 



