174 



NATURE 



\_yune 19, 1879 



THE ELECTRIC DISCHARGE WITH THE 

 CHLORIDE OF SILVER BATTERY 



■jVTESSRS. De La Rue and Miiller, in the second 

 -'■'-'- part of the researches which they have carried on 

 during three and a half years, have contributed facts of 

 the highest value towards the solution of the problem 

 presented by the beautiful* phenomenon of stratification 

 produced by electric discharges in vacuum tubes. The 

 following are some of the more important results of these 

 experiments as described by the authors." 



These phenomena, first noticed by M. Abria in 1843, 

 were independently re-observed by Mr. (now Sir William) 

 Grove in 1852, and have since engaged the attention of 

 many physicists. The late Mr. Gassiott, working at first 

 with an induction coil, but more recently on the same lines 

 as the voltaic batteries of high potential,^ published results 

 of great interest; while, on the other hand, Mr. W. 

 Spottiswoode is still pursuing with great acumen and 

 originality a similar investigation, both with the induction 

 coil and the Holtz machine, with which he has recently 

 used condensers of great capacity. 



Throughout our labours we have felt so strongly the 

 necessity of obtaining numerical results as data for the 

 foundation of a theory, that we have not hesitated to risk 

 much in this cause. By the fusion of terminals, or the 

 sudden discharge of the condenser, we have lost a vast 

 number of very beautiful tubes ; but gradually by the 

 adoption of various devices, and by the employment of 

 instruments specially constructed and insulated to suit the 

 high potentials we deal with, we have succeeded in over- 

 coming the various impediments, so that we can now 

 readily obtain values for the physical quantities that 

 enter into consideration in our experiments. 



There is a serious trouble connected with the study of 

 the discharge in rarefied gases, for, after a very short 

 time, the tubes completely and permanently change, so as 

 no longer to present the splendid stratifications witnessed 

 on a first trial. We believe these changes occur much 

 more rapidly with the battery in consequence of the greater 

 amount of current, than with the induction coil ; but the 

 fact appears to have been well known to Dr. Geissler, of 

 Bonn, who, on the occasion of a visit to our laboratory, 

 brought with him some tubes through which no current 

 had previously passed (virgin tubes, as he called them), 

 which presented most beautiful phenomena lost for ever 

 after too brief a period. 



Tube 123 (cyanogen), for example, when first connected 



with the battery, presented strata which completely fille 1 

 the tube without leaving a dark space near the negative, 

 some threading themselves on it, as shown on the left ot 

 Fig. I ; but after a few seconds the strata widened oit rs 

 on the right hard t £;ure, then other changes occurred, t d 

 the first phases h.ve never been reproduced. 



UBS !23. 



Fig. 



Another case is presented by the nitrogen tube Fig. 2, 

 the right-hand figure showing the first phase, and the 

 left-hand figure a second phase, which in its turn has for 

 ever disappeared, and has been replaced by the ordinary 

 disk-form of strata. 



Fig. 2. 



After spending much time in experiments with tubes 

 prepared for us by Dr. Geissler, Messrs. Alvergniat 

 Fr6res, of Paris, and Mr. Hicks, of Hatton Garden, with 

 the vexation of finding that we could not often enough 

 repeat our experiments, we ultimately came to the con- 

 clusion to have others made, but not exhausted, and to 

 perform ourselves the charging and exhaustion. The 

 tubes we usually employ have a glass stop-cock fitted to 

 them at each end ; they are 32 inches long, and from 175 

 to 2 inches in diameter ; the terminals are of aluminium, 

 and about 29 inches apart, one being a ring, the other a 

 wire bent at a right angle, so as to point in the direction 

 of the axis of the tube (see No. 144, Fig. 3), for we have found 

 that the phenomena vary according as the ring or wire is 

 made positive. 



^ 



tJ^ 



Hi 



"V. 



y^ 



^y=^ 



Fig. 



These we exhaust and fill with any gas we may wish 

 to experiment with, and gradually exhaust again, noting 

 the phenomena presented at different pressures, with i 

 different potentials, and with different amounts of current. ] 

 We re-fill and exhaust the tube again and again, and 

 mostly obtain, under the same conditions, as nearly as 

 possible the same phenomena, of which we are careful to 

 make sketches and, if possible, to obtain photographic 

 records. 



In some cases we make use of tubes provided with a 



' See Phil. Tfnns.y vol. cJxix., pp. 55.121. i 



*_^ Mr. Gassiott made several batteries of dLfierent kinds in the course of 1 

 his experiments : on the occasicn of a visit to his laboratory, January 26, 

 1875, the current of his Leclanche battery was measured by us with a volta- 

 meter. The current of 1000 new cells was fcund to be o"o7464W: that of 

 the whole 3000 cells', 1000 of which had been a li ng-time in use, o'047i8 W- 

 laking the Leclanch^ as i"48 volt the internal resistance of the new battery 

 must have been i9"83 ohms per cell ; that cf the whole 3000, 31 "87 ohms per 

 cell, '1 he striking distance of the whole 3000 between a conical point and a j 

 disk o'i25 inch diamet*r was only o'i25 inch; whence the inference is that 

 the insulation was, at that time, imperfect. 



calibrated chamber between two stop-cocks, as n—b, No. 

 145, Fig. 4, the chamber in this particular case having 7^Qt\\ 

 of the capacity of the tube, this tube has also an absorption 

 chamber communicating through a cock and intended to 

 contain spongy palladium. After a tube has been ex- 

 hausted so as to produce a particular phase, and in 

 the course of the experiment the exhaustion has been 

 carried beyond that degree which permits of the reproduc- 

 tion of that phase, one or more charges of gas may be 

 successively admitted into the tube by filling the calibrated 

 chamber with gas at any particular pressure, and then 

 opening the stop-cock communicating with the tube ; the 

 lost phase is thus reproduced. 



The apparatus which we have found it advantageous to 

 adopt for the exhaustion of our tubes is shown in Fig. 5 ; 

 it comprises three means of exhaustion which ,Trc succes- 

 sively employed as the vacuum becomes more perfect. 

 The first is an Alvergniat high-pressure water iroinpe in 

 connection with the high-pressure water-main of the 



