"Now I understand."
"Ah! then we are to escape this time without the 'Mariner's March.'"
"It appears, Master Jack, that you have turned philosopher as well as your brothers. Can you tell me what causes lightning?"
"Yes, I can, Willis. You must know, in the first place, that all the layers of the atmosphere are, more or less, charged with electricity."
"Ask him how," said Fritz drily.
"Ah, you hope to puzzle me," replied Jack, "but thanks to Mr. Wolston, I am too well up in physics to be easily driven off my perch, and therefore may safely take my turn in philosophising."
"Well, we are listening."
"The air, by means of the vapor it contains, absorbs electricity from terrestrial bodies, and so becomes a sort of reservoir of this invisible fluid. All chemical combinations evolve electricity, the air collects it and stores it up in the clouds. There, worshipful brother, your question is answered."
"Good, go on."
"Well, Willis, you must know, in the second place, the clouds are very good fellows, and share with each other the good things they possess. When one cloud meets another, the one over-supplied with this fluid and the other in its normal state, there is an immediate interchange of courtesies, the negative electricity of the one is exchanged for the positive of the other."