"Yes, sir, but that is different."
"But the principle is the same; can you tell me why?"
Both the boys looked puzzled.
"It is only because the wood does not weigh so much as water; neither are the stones as heavy as mercury, therefore they cannot sink."
"I wish we could go into the mines. Can't you take us, sometime, grandpa?" said Harry.
"That is asking rather too much, my child, for quicksilver is not a common metal. There are in the world only four important localities from which it is obtained. These are California, Peru, Austria, and Almaden in Spain. The mines nearest us are in California. I think I shall never go as far as that, but I hope you both may before you reach my age.
"It is a curious story how the mines in Peru were discovered. Cinnabar, when ground very fine, will make a beautiful red paint. The Indians used this to ornament their bodies on grand occasions. This caused the country where they lived to be examined, and the cinnabar was found. The Romans used this paint hundreds of years ago in decorating their images and in painting pictures. It is very highly valued now, and we call it vermilion."
"Fred," continued Mr. Lenox, "you spoke of the difficulty of separating gold and silver from the rock in which they are found. Did you know that our wonderful mercury renders valuable aid in this? The rock that contains the precious metal is crushed fine, sifted and washed until as much as possible of the gold or silver is removed; then it is placed in a vessel with the quicksilver, which seems immediately to absorb it, thus separating it entirely from every particle of sand or rock. If the metal to be cleansed is gold, you will see a pasty mass or amalgam, as it is called, of a yellowish tinge. This is heated, and the mercury flies away, leaving behind it the pure gold."
"How did people learn to do this?" asked Fred.
"They did not learn it all at once. It was only by years of patient effort and frequent failure that they finally succeeded.