[Illustration: _Chemist & Druggist_]
The physician writes his prescription, and it is then sent to the shop
of the druggist, who makes it up according to the order. Several of
their medicines are rendered expensive, by having musk, camphire, and
other dear articles introduced in them. Apothecaries Hall is the best
place to buy drugs, for they never vend any that are not genuine."
"Drugs are composed of minerals as well as vegetables, are they not,
papa?" said Theodore.
"Yes, my dear boy. But do you perfectly comprehend what is a mineral?"
"A mineral, papa, is a semi-metal, as they are called by the chemists,
such as antimony, zinc, bismuth, and others. They are not inflammable,
but are hard and brittle, and may be reduced into powder. Mercury or
quicksilver has been classed with semi-metals. Shall I tell you how
many metals there are, papa?"
"If you please Theodore."
"There are six, papa. Gold, silver, copper, tin, lead, and iron. The
most precious metals, such as gold and silver, do not form the most
splendid ones. The pyrites, which are a mixture of iron and sulphur,
are more beautiful to the eye."
"Very well remembered, Theodore. But you forget to class the magnet as
a mineral."
"I do not perfectly understand the nature of the magnet, papa."
"It is a species of Iron found in iron mines," said Mr. Durnford,
"which has the singular property of attracting metal. The ancients
knew no means of finding their way at sea, but by the stars; of
course when those celestial bodies were not visible, the sailor was
frequently at a loss how to steer. A piece of steel is now procured,
made something like a needle, but flat, about four inches long; this
is rubbed with the loadstone, and then balanced exactly on two points
or pivots, so that it may turn round freely. This needle when
fixed in a box, is called the mariner's compass, and as it invariably
turns toward the North, the sailors can now steer to any part of the
world, which they could not do without the help of this piece of
iron. The first knowledge of this useful application of the magnet
is supposed to come from Marco Polo, a Venetian, in the thirteenth
century; but it is said to have been known to the Chinese."
"We will now take a view of those