"The ore is first broken up into small pieces, and mixed with quicklime. It is then put into large retorts and heated. A retort, you know, is a closed vessel, with pipes leading from it.""I think I can tell why this is done," said Norah. "The sulphur would soon melt into a liquid, and boil, and then it would pass away along the pipes in the form of vapor.""That"s just it," said Will. "But we have already learned that the mercury too would boil and pass away in vapor. This mercury vapor must not be lost. It is wanted.
"Some earthenware pipes are therefore fixed to the retorts, and the vapor is made to pass through them. As these pipes are kept cool, the vapor condenses on the sides in little round, silvery balls, and nothing more need be done than to collect them, and pour off the liquid metal ready for use.
"Suppose I tell you now," he continued, "some of the uses to which mercury is put.
"One of the most important uses is in separating gold and silver from the ores in which they are found.
