VOLTAIC El 





VOLTAIC ELECTRICITY, VII. 



TUX > : IN EXHAUSTED 



iiKS HRATINU t: K THE CUERBMT MOl 



FIKINO OHDNANCS fl'/Ktf. 



IT would I-- quite impossible, in the paoe at oar diapoaal, to 

 (fire even a briuf list of the n .1 of electric regulators, 



or lumps, wlu.-h hare been r.-M-. t trout time to time. ThoM 

 who iiro interested in the subject would do well to pay a vimt 

 t.< thf I'.it.-nt oflioe, and examine th-e the apeoifloations relat- 

 ing to tlu< < !, tn<- litfht. Among these patented contrivances 

 are seen MKUIV whi.-h are totally impracticable, but moat of 

 tin-in rxliil'.t -real iiiKi-miity all the tame. 

 pri-iili .inty f our patent law, pemona 

 .-.in patent ideas which hare been patented 

 iimro than once before on the 



. iition that they pay the noceitarj 

 feee and the effect of this bad lyttem in 

 ai'i-ii in |irrt,Ttion in those specifications 

 n-Uitinj: to i-lci-tric litfht regulator*. The 

 t.vo carbon rods which form the electrode*, 

 which the arc light is produced, 

 hare, by sanguine inventors, been placed 

 in every conceivable position, but the 

 natural law which compels the survival 



fittest has affected these regulators 

 as it has other things, and the favoured 

 position is still that adopted in the old 

 Serriu lamp. Thus in the most modern 

 forms of arc lamps, such as the Brush, 

 the Crompton, and the Pilsen regulators, 

 we still find the carbon rods placed ver- 

 tically, and the arc produced between 

 their points. There is among modern 

 regulators a notable exception to this rule, 



n ted by the Jab loch koff " candle," 

 which caused a few years ago, when it 

 was first introduced, such a panic araon r 

 holders of gas shares. In thie so-called 

 electric candle, the two carbon rods stand 

 side by side, instead of being one above 

 the other, and they are separated by a 

 strip of plaster of Paris, or other insulat- 

 ing material, which is destroyed by the 

 heat of the electric arc as the " candle " 

 burns down. This clever and simple con- 

 trivance will be more fully described when 

 we come to consider, later on, the more 



modern applications of electricity ; but a reference to it is 

 necessary in this place, as it is, strictly speaking, an arc 

 light 



That the electric arc is not dependent in any way for its 

 support upon the oxygen of the atmosphere may be proved by 

 the fact that it can be maintained under the exhausted receiver 

 of an air-pump. A gas flame, on the other hand, is altogether 

 dependent upon oxygen, and an ordinary bat's- wing burner 

 will consume in one hour as much of this life-supporting 

 principle as five human beings, givin? back, in exchange, deadly 

 carbonic acid. For this reason electricity affords a light which 

 does not poison the air. But it must not be supposed that no 

 heat is given off by the electric arc ; on the contrary, it exhibits 

 the moat intense heat which it is possible to produce, far 

 greater, in fact, than that of any form of ordinary furnace ; 

 but the heat being confined to the comparatively small space 

 between the electrodes, the surrounding air is not nearly o 

 much affected as in the case of a gas flame. Dr. C. W. Siemens 

 has taken advantage of the intense heat of the electric arc in the 

 eonstruction of his electric furnace. This consists of a crucible, 

 through the bottom of which one electrode is carried, whilst 

 the other meets it inside by being pushed through a hole in the 

 lid. In this furnace 8 Ibs. of platinum can be reduced to a liquid 

 state in fifteen minutes. 



There is another way in which the luminous effects of the 

 electric fluid may bo seen, and that is by causing what is called 

 an induced current to pass through an exhausted glass tube. 

 The apparatus employed for this purpose is known as an 

 Induction Coil, and will be described in a future lesson. Fig. 38 

 will give a faint idea of this light. A is an exhausted glass 

 123-N.E. 



tube hermetically sealed, pUoes of jilitliia wire beta* faaed 

 into it at two different parts, A, . for UM earreat to eater. 

 Inside A is a goblet O. made of nraninai giaee. Aa wo* a* 

 the wire* fro* the coil are WDM**! with the pUssaaaa 

 wine, the whole interior of 4 beoomee highly lamtnoae, the 

 ffoblet appearinff to be running over with liquid Are. In a 

 dark room thie ia aa exqoieheJy beeati/ol erpsrianat 



We mart now pass on to notice the MS* elaes of al<i 



prodaoed by the current. These are the caloric or kmttrng 



tii-t are very easily observed : if we are working with 



a large number of batteries, and the oondscting wtra U 



mall, it will MOD beoome eo hoi thai it eaaaot be hssilM 



with any defree of comfort. 



Thia heating property of eleotrioitr 

 appears only to be developed when the 

 wire along which it U f iilij is too 

 mall to conrey H properly. lisa-Be a 

 heated wire ia a sot* tin that ft fa too 

 email, and thai, therefore, a portion of 

 the power U lost by being convert*! 

 into heat, instead of doing the work 

 required. When, however, oar objest is 

 to show the heating power, a* email a 

 wire aa possible Is ehoasa for the per- 

 pose. The abook from a large battery 

 of Leyden jars will be found saliniiat to 

 deflagrate a fine iron wir* 1 , bat the Tol- 

 tsio current answers much bettor, and 

 is wore easily applied. If we take a 

 piece cf very fine platinum wire, and 

 having wound on* end of it round the 

 scraped end of one of the battefj wires, 

 we bring another part of it against the 

 other battery wire, we shall soon fad 

 that it becoroee heated. By (lipping the 

 wire gently along, so as to diminish the 

 length of the platinum that ia ineladed 

 in the circuit, it will first laeomi red- 

 hot, then white-hot, and ultimately wil.' 

 rn-it. The length of wire that oaa ia 

 this way be maintained at a red heat 

 varies with the power of the battery; 

 three or four feet may, however, be easily 

 ignited, and much greater lengths ban 

 been rendered luminous. 



Thia experiment is best shown in tht 

 way represented in Fig. 39. Two braai 

 rods, A and B, are fixed vertically on 

 round stands ; at the top of thee rods are binding screw*, 

 by which the fine wire may be held and adjusted for length. 



The battery wires are put through holes in A and a, or may 

 be simply twisted round them, and thus all danger of burning 

 through the platinum is avoided. 



Aa soon as the current ia caused to pass along the wire 

 it becomes luminous, and at the same time expands, dropping 

 in the middle, and thus affording further proof of the 

 produced. When the current ia interrupted, the wire at 

 cools and contracts. Jf a chain composed of alternate links 

 of silver and platinum wire be placed 

 between A and B, the platinum links 

 will become luminoua ; but, as the 

 silver ia a better conductor, the 

 links of that metal will retain their 

 ordinary colour. 



As the heating effect arises from 

 the quantity of electricity, and not 

 from its intensity, the best results 

 will clearly be obtained when the 

 batteries are set up side by aide ; 

 all the zincs being connected to- 



38. 



Tig. 9. 



gethcr for one pole, and all the platinums for the other. 

 The battery known as Hare's Deflagrator is the best for this 

 purpose. It consists of long strips of copper and sine, sepa- 

 rated by a hair rope and wound round into a spiral soil 

 In this way a great quantity of electricity of small toassoa 

 ia produced. The exciting liquid used for it is dilate sal- 

 pburic acid. 

 The heating properties of the electric current are 



