Page:Twenty Thousand Verne Frith 1876.pdf/115

 reply. Do not the elements you employ soon expend themselves? Zinc for instance. How can you replace it if you have no communication with the land?”

“Your question shall have an answer,” replied Captain Nemo. “I may tell you, however, that mines of zinc, iron, silver, and gold, all exist at the bottom of the sea, and the exploration of them is surely practicable. But I am in no wise indebted to the minerals of earth, and I only ask the sea to produce my electricity!”

“The sea!”

“Yes, and the means are these. I have been able to establish a circuit between the threads, cast in different depths, to obtain electricity by the difference of the temperature they underwent, but I prefer an easier plan.”

“And that is?”

“You know the composition of sea-water. In 1,000 grammes there is 96½ per cent. of water; two and one-third per cent. of chloride of sodium, then small quantities of chlorides of magnesium and potash, bromide of magnesium, sulphate of magnesia, sulphate and carbonate of lime. So you perceive that the chloride of sodium is present in a large proportion. Now, it is this sodium which I extract from the water, and of which I make my elements.”

“The sodium?”

“Yes. Mixed with mercury it forms an amalgam, which takes the place of the zinc in the Bunzen elements. The mercury remains, the sodium only gives off, and the sea itself furnishes that. I may tell you, moreover, that the sodium battery may be considered as the most