"Every metal except lead."
Delcassé turned this over for some moments in his mind.
"If that had been the cause," went on Lépine, at last, "there would have been other explosions, many of them—and our navy would not have been the only one to suffer. The whole atmosphere is charged with such waves, of every length and every degree of intensity."
"Perhaps you are right," agreed the Minister. "What was the fourth theory?"
"The fourth theory was that finally adopted by the board. It was that a certain kind of powder, known as 'B' powder, degenerates under heat, and becomes, in time, extremely combustible, so that it will sometimes explode apparently without any exciting cause."
"In what manner was the truth of this theory demonstrated?" demanded Delcassé.
"In a most convincing manner. A certain amount of this powder, which the board was examining, did explode in this way, under their very hands. Had the amount been larger, not a member of the board would have escaped. But, sir, you know all this as well as I."
"I wish to refresh my memory," Delcassé explained. "I wish to see if your memory, which I admire so much, agrees with mine. Now tell me this: what was done to prevent a recurrence of such an accident?"
"The powder in all French magazines was overhauled, and that which there was any reason to suspect was destroyed. To prevent future deterioration, the magazines of all our battleships were equipped with a special cooling apparatus. In this, we were soon followed by all other nations."
"And yet," said Delcassé, in a low voice, "the latest and best of our battleships blew up this morning!"