TUB ELECTRIC LIGHT.] 



UNDULATORY FORCES. LIGHT. 



135 



announcement that voltaic electricity might be made the 

 means of producing a very pure and intense light ; and 

 several patents have been taken out for the purpose of 

 accomplishing this. Indeed, many exhibitions of the 

 light have been made at several public institutions, and 

 also in the open air, by which the sanguine hopes of its 

 originators have been apparently increased. Of late, 

 however, little has been heard of the subject beyond the 

 few remarks which occasionally fall from men of science 

 in their discourse upon it. 



The idea of employing electricity for this purpose is 

 not novel; for the power of the voltaic light was 

 thoroughly investigated in the time of Sir Humphry 

 Davy : but the difficulties which electricians had then to 

 contend with in the inconstancy of the galvanic battery, 

 offered an insurmountable barrier to its use. A part of 

 this difficulty was overcome by the late Professor 

 Daniell, who was the first to contrive a constant battery. 

 Since then, the voltaic arrangements, by which a current 

 of electricity of great power may be sustained for any 

 length of time, have been improved by Mr. Smee, Pro- 

 fessor Grove, M. Bunsen, and the Rev. Professor Callen, 

 of Maynooth ; so that, at the present time, there are 

 abundant facilities for producing the light. 



The first patent which was taken out for the use of 

 electricity for illuminating purposes, was that of Mr. 

 Staite, in November, 1846. In July, 1848, he obtained 

 another patent for an improved form of battery. This 

 he called the perflitent battery, in contradistinction to 

 the percolating, which was already in use. It was thus 

 naiM-d on account of the arrangement which he adopted 

 for keeping up a supply of acid. The troughs, or cells 

 j battery, communicated with each other by means 

 of elastic syphons or cross tubes, and the acid was made 

 to flow from cell to cell throughout the entire length of 

 the series ; so that, when it arrived at the last cell, it was 

 completely exhausted of its exciting power, and satu- 

 rated with zinc. It was thought that such an arrange- 

 ment would be the means of economising power and 

 material ; but it happens to bo the very worst that could 

 possibly have been contrived for such a purpose. The 

 electrician knows, that if he requires the greatest power 

 from his battery, each of the cells must be acting alike, 

 and to their fullest extent ; for it is the condition of 

 electricity to multiply itself^ not after the ratio of the 

 most powerful cell, but after that of the weakest. If, 

 therefore, we have in the arrangement a number of cells 

 working unequally, as is the case in the perfluent 

 battery, the activity of the one set of cells will be of no 

 avail in raising the inactivity of the other ; for the least 

 powerful cell governs all the others, and reduces them 

 to its own standard. It follows, therefore, that the last 

 cells in Staite's arrangement must act as clogs on the 

 first ; for, as they are almost without action, they must 

 reduce the power of the first cells to little or nothing. 

 Another alteration, proposed by Mr. Staite, was, that a 

 liquid amalgamation of zinc and mercury should be used 

 in bags, or porous cells, in lieu of the ordinary form of 

 amalgamated zinc. He also suggested the use of a solid 

 amalgam, consisting of o of zinc and 1 of mercury. He 

 likewise proposed that lead should be employed instead 

 of zinc, in order that valuable products might be ob- 

 tained. All these suggestions, however, are of no value ; 

 for they are contrary to the principles on which a good 

 galvanic battery ought to be constructed. 



In July, 1848, the Chevalier Alexandre Edonard 

 Lemolt also took out a patent for improvements in the 

 batteries and apparatus used in obtaining the electric 

 light. His improvements in the battery were but modi- 

 fications of those long since adopted by Professor 

 liunsen. He employed plates of carbon, which were 

 either cut out of the hard coke which lines the interior 

 is retorts, or else formed by powdering the coke, 

 mixing it with a little coal-tar, then pressing it into a 

 mould, and baking it at a low red-heat. Since then 

 namely, in the month of February, 1849 Mr. Chiirlcs 

 Thomas Pearce obtained another patent for improve- 

 ments of a like description. His battery was a perfluent 

 onu, and it differed from Staite's in the circumstance 



that the flow took place separately in each cell, and not 

 from cell to cell ; so that the amount of power generated 

 in each cell was the same, and his porous diaphragms 

 were made of sycamore wood, soaked in dilute acid. 

 Another of his claims was the use of alkaline salts in 

 solution, which did away with the necessity for amalga- 

 mating the zinc. Lastly, another patent has since this 

 been obtained by Messrs. Staite and Petrie, wherein 

 they recommend a modification of their former arrange- 

 ment, so as to keep the liquids in all the cells of the 

 same degree of strength. Each of these patentees has 

 likewise secured to himself the use of certain contri- 

 vances, whereby the charcoal-points which emit the light 

 shall be removed and kept at a proper distance from 

 each other. These, in fact, constitute the real claims to 

 consideration ; for the batteries which they have in- 

 vented are not worthy of the least attention. 



Batteries used in obtaining the Electric LigM. 

 (a.) DanieWi Battery, which consists of a jar containing 

 a cylinder of sheet copper, and a saturated solution of 

 its sulphate ; within this there is placed a porous cell 

 (composed of brown paper, unglazed earthenware, or 

 bladder), which holds a cylinder of sheet zinc, and 

 dilute sulphuric acid. These are arranged so as to 

 obtain both quantity and intensity of electricity. 



(6.) G-rove's Battery is constructed in a very different 

 manner. The outer cell is of an oblong form, and it 

 may be made of glass, earthenware, or gutta-percha. It 

 contains a piece of sheet zinc bent into the form of the 

 letter U. one leg being a little longer than the other. 

 The zinc is amalgamated according to Mr. Smee's plan, 

 by dipping it into dilute sulphuric acid, and then cover- 

 ing it with quicksilver. Within the bend of the zinc 

 there is placed a porous oblong cell of unglazed earthen- 

 ware, and within this a sheet of platinum. The battery 

 is set in action by pouring dilute sulphuric acid (in the 

 proportion of one acid to seven water) into the zinc com- 

 partment, and strong nitric acid into the platinum cell. 

 As before, the battery may be arranged for quantity as 

 well as intensity. 



(c.) Butuen's Battery, as well as that modification of it 

 proposed by M. Lemolt, is truly a Grove's battery, with 

 a piece of charcoal instead of a sheet of platinum. 



('/.) The Maynooth Battery, which was contrived by 

 the Rv. Professor Callen, of Maynooth, is also a modifi- 

 cation of Grove's principle ; for a plate of cast-iron 

 is used instead of platinum ; or a cast-iron cell is 

 charged with a mixture of two parts of strong sulphuric 

 acid, one-and-a-half of nitric acid, and the same of 

 water ; and it is better to excite the zinc with a strong 

 solution of muriate of ammonia instead of with dilute 

 sulphuric acid, for this does away with the necessity for 

 amalgamating the metal. 



Professor Grove says that the result of his experience 

 is, that the nitric acid battery, in one or other of the 

 preceding forms, is the only one, liitherto invented, 

 which otters anything like a practical means of applying 

 this power to illuminating purposes; and the best 

 arrangement that can be adopted for obtaining the 

 greatest amount of power, is to use about forty or sixty 

 tells, arranged in two series of twenty or thirty each. 

 By this means we have the quantity of two cells, and 

 the intensity of twenty or thirty. If we go beyond this 

 in the intensity arrangement, the fluids in the cells 

 begin to boil, and quickly to evaporate. This is objec- 

 tionable ; for it not only renders the atmosphere of the 

 room irrespirable, but it frequently brings the action of 

 the battery to a standstill. The source of power in all 

 cases is the chemical action which takes place in the cells. 



Mode of nlifiiinhii/ the Light. The wires which convey 

 the electricity from each of the series must be con- 

 nected, BO that the two positive poles are brought 

 together, and the two negatives. The wires should be 

 of large size, so as to conduct the electricity with ease ; 

 and they should be covered with gutta-percha, so as 

 to insulate them. If this precaution be not taken, 

 they may touch each other, and so cut off the current ; 

 or they may become unmanageably hot ; or they may 

 communicate a shock to the operator. II is usual to 



