Intelligence and Miscellaneous Articles. 285 



ON SOME EXPERIMENTS WITH THE SPARK OF A LARGE 

 BATTERY. BY A. RIGHI. 



The battery which I have had made and which has given me the 

 best results, consists of 108 condensers. Each of them is a cjdin- 

 drical beaker more than half a metre high, and 16 centim, in 

 diameter. The coating extends to about half the height, and 

 each has a surface of about 1432 square centims. The glass is 

 rather more than a millim. thick, and, accordingly, the capacity of 

 each beaker is about 6270 electrostatic units (C. Gr. S.). The 

 arrangement of the conductors of the battery is that desci'ibed in a 

 memoir on the electric spark, published by myself in 1875. 



The 108 jars are arranged in 6 batteries of 18 each arranged in 

 cascade, by which high potentials can be obtained. The terminal 

 coatings are connected with the conductors of a Holtz machine, 

 and the armature of the middle is put to earth. It has thus the 



same capacity as if ^ = 3 jars together were joined as a battery, 



with the armatures directly communicating with two conductors of 

 the machine ; hence the capacity of the system will be 18,810 

 electrostatic units (C. G. S.), or about J^- of a microfarad. 



The Holtz machine is like one which I have described else- 

 where*, but has four disks. It ordinarily gives sparks more than 

 30 centim. in length ; and this even on the most humid days, for it 

 is enclosed in a glass case containing chloride of calcium, together 

 with a small frictional machine to give the initial charge. The 

 disks are unvarnished, and it is sufficient to clean it from time to 

 time with alcohol to obtain the best results. 



It happened more than once that the battery discharged through 

 the machine, leaving deep marks on the disks, and one discharge 

 even perforated two of the large sides of the glass case. In order to 

 prevent these evils, and also for the protection of the person who 

 worked the machine, I connected the two conductors and the ter- 

 minal coatings of the battery by a long glass tube filled with water. 

 With this arrangement, if the discharge took place in the machine 

 it could not do any damage, nor be dangerous, for there is a very 

 high resistance in the circuit. The connexions with the apparatus 

 in which are produced the discharges to be studied are metallic, 

 being made with long wide brass tubes. 



This battery, which has served me for experimentally illus- 

 trating a special course on atmospheric electricity, gives on a 

 still larger scale the remarkable effects which I have elsewhere 

 described f. For instance, if in the circuit we place two brass 

 spheres 6 to 7 centim. in diameter, at distances of 5 to 10 centim. 

 apart, and place beween them a flat strip of glass 5 metres long or 

 more, coated with zinc-filings like the magic pane, we obtain on 

 the strip, instead of the usual luminous ramifications, a loud and 



* Deso'izione ed uso di una viacchina ^c. suH Ace. di Bologna, 1879. 

 t Loc. cit. 



