210 Royal Society : — Messrs. De La Hue, Miillcr, and 



voltameter having a resistance of 11 ohms. The striking-distance 

 of 1080 elements between copper wire terminals, one turned to a 

 point, the other to a flat surface, in air is ^^ ¥ inch (0*096 millim.) 

 to tt^jj inch (0-1 millim.). The greatest distance through which 

 the battery-current would pass continuously in vacuo was 12 inches 

 (30*48 centims.) between the terminals in a carbonic acid residual 

 vacuum. This battery has been working since the early part of 

 November 1874, with, practically, a constant electromotive force. 



Besides 2000 more cells like those just described, we are putting 

 together 2000 cells, with the chloride of silver in the form of 

 rods, which are cast on the flattened silver wires, as in a battery 

 described by De La Rue and Miiller*, but in other respects 

 similar to the battery above described, the glass tubes being, how- 

 ever, somewhat larger in diameter; the rods of chloride of silver 

 are enclosed in tubes open at the top and bottom, and formed of 

 vegetable parchment, the object of these vegetable-parchment cases 

 being to prevent contact between the zinc and chloride-of-silver rods. 

 The internal resistance of batteries so constructed is only from 2 

 to 3 ohms per cell, according to the distance of the zinc and chloride- 

 of-silver rods, and they evolve from 3 to 4*5 cub. centims. (0*18 to 

 0*27 cub. inch) per minute, in a voltameter having a resistance of 

 11 ohms. Their action is remarkably constant. 



For the experiments detailed below, vacuum-tubes were generally 

 used of about 1| to 2 inches (3*8 to 5 centims.) in diameter, and from 

 6 to8inches (15*24 to 20*32 centims.) long ; also prolate spheroidal 

 vessels 6 inches by 3 inches (15*24 by 7*62 centims.). The termi- 

 nals are of various forms, and from 4 inches to 6 inches (10*16 to 

 15*24 centims.) apart, and made of aluminium and occasionally of 

 magnesium and of palladium, the latter showing some curious phe- 

 nomena with a hydrogen residual vacuum, Avhich will be described 

 in a future paper. A tube which has given the most striking results 

 is 8 inches (20*32 centims.) long, and has a series of six aluminium 

 rings varying in diameter from § of an inch to about 1| of an inch 

 (0*05 to 3*17 centims.), the thickness of the wire being about ^L- 

 (0*16 centim.) of an inch ; the rings are a little more than 1 inch 

 (2*54 centims.) apart; and connecting wires of platinum pass 

 through the tube from each ring and permit of the length and other 

 conditions of the discharge being varied. 



At times the terminals of the battery were placed in connexion 

 with accumulators of different kinds — for instance, two spheres of 

 18 inches (45*72 centims.) in diameter, presenting each a superficies 

 of 7*07 square feet (65*68 square decims.), and cylinders of paper 

 covered with tinfoil, each having a surface of 16 square feet (148*64 

 square decims.) ; the globe and cylinders were in all cases carefully 

 insulated. Other accumulators were composed of coils of two 

 copper wires yL of an inch (0*16 centim.) in diameter, covered with 

 gutta percha, in two folds, -^ of an inch (0*08 centim.) thick. 

 One coil contains two wires, A A' and BB' (fig. 1), coiled side by 



* Journal of the Cbem. Soc, 2nd series, vol. vi. p. 488 ; Comptes Eendus, 

 1886, p. 794. 



