394 



ously shown with the former) spark discharges passed between two 

 terminal copper plates through the air, before the completion of the 

 circuit. 



The well-known luminous arc in air, as is usually obtained from 

 an extended series of the nitric-acid battery, was very brilliant, but 

 from the small size of the porous cells (3 inches long, g inch broad) 

 containing the nitric acid, it was only tried by a momentary action. 

 With the water-battery I have never been able to obtain a continuous 

 discharge in air similar to the voltaic arc ; whether from points or 

 plates, the discharges from this battery are invariably in the form of 

 minute clearly defined, and separated sparks. 



Although the water-battery consisted of nearly nine times as many 

 metallic elements as the nitric-acid battery, it exhibited by the gold- 

 leaf electroscope very little increased signs of tension. 



This is in accordance with the results obtained by me in 1844, when 

 I showed that the tension of a single cell increased in force according 

 to the chemical energy of the exciting liquid. " In all the experi- 

 ments I made, the higher the chemical affinities of the elements used, 

 the greater was the development of evidence of tension "(Philosophical 

 Transactions, 1844, part 1. p. 52). 



Recently, through the kind introduction of Professor Wheatstone, 

 I have had an opportunity of experimenting with 512 series of 

 Daniell's constant battery, and my present object is to present to the 

 Royal Society a short account of the results I have obtained, and to 

 describe the appearance and character of the voltaic discharge of 

 these several batteries when taken in vacua. 



The vacuum-tubes I used were prepared by means of carbonic acid 

 (Philosophical Transactions, 1859, part 1. p. 137). For the sake of 

 reference I will denote these by the original numbers which I am 

 accustomed to attach as the vacua are completed : in the following 

 experiments these were 146, 187, 190, 196, 202, and 219. 



No. 146 is 24 inches long and 18 inches in circumference, and has 

 a copper disc 4 inches diameter at one terminal and a brass wire at 

 the other : this vessel is figured in my last communication. No. 187 

 and 196 (see fig. 1) are each about 6 inches long and 1 inch 

 diameter, with gas-coke balls | inch diameter, attached to the 

 hermetically sealed platinum wires, the wires being protected by glass 

 tubing as far as the balls, placed inside the tube 3 inches apart. 



