Fig. 192.
De la Rue discharger, containing a series of six pairs of different substances, such as charcoal, iron, lead, zinc, copper, antimony, in six pair of crayon holders, and turning on a centre, so as to be changed at pleasure.
Fizeau and Foucault have made a careful comparison of the light obtained from 92 carbon couples as arranged in a Bunsen's battery, and of the oxy-hydrogen, or Drummond Light, as compared with that of the sun, and they state that "On a clear August day, with the sun two hours high, the electric light (assuming the sun as unity) bore to it the ratio of one to two and a half—i.e., the sun was two and a half times more powerful, while the Drummond Light was only 1/146th that of the sun." Bunsen found the light from 48 carbons equal to 572 candles. In Bunsen's battery carbon is substituted for the platinum in Grove's arrangement; and simultaneously with Bunsen, Cooper (in England) had applied charcoal for the same purpose.
At night the giant ship (Polyphemus like) is to have an electric light at the mast-head whilst steaming across the Atlantic.
Fig. 193.
Great Eastern, with electric light.