Lafond was attentive enough to this. He desired above all the practical knowledge.
"Observe the fumes," said Durand; "that is the true test. When they whirl above the molten metal, then is everything well. When the fumes do creep slowly like the mist on a stream, then the heat is not sufficient. If, on the other hand, they do rise straight upward, then it is necessary to reduce the heat at once."
After a time the remaining impurities, under Durand's skilful manipulation, were absorbed by the cupels. The little vessels were drawn from the furnace and placed to one side to cool. A small yellow button was finally detached with pincers.
"That then is the gold!" cried Lafond.
"And silver," corrected Durand gently. He weighed the button with great care. Then with nitric acid he ate out the silver. The result was weighed. The assay was finished. By comparing the weights of the original ore, the cupelled button and the final product, statistics were obtained.
The men drew a long sigh of relief now that the task was quite finished.
"It is hard work," observed Durand.
"It is very good of you to take so much trouble for me," replied Lafond, for the sake of politeness.
"I like you," explained the old man simply, "because you speak French and because there is something in your face that shows that you too have been wronged, and that perhaps, like myself, in your youth you have been light-hearted and were loved by maid and man with the love that is given the reckless—and foolish," he concluded with a little bitterness.
Inexplicably this appealed to Lafond, so that he almost wept with the sheer joy of it.