to be obtained. They got it at first from Demerara, in South America;
homeward-bound ships brought it as ballast. But the War of 1812
interfered with commerce, and compelled them to look at home for their
sand, as for many other things. At first they used the sand of Plymouth
Beach, until better was found at Morris River, in New Jersey. But a few
years ago sand of the first quality turned up in Berkshire County. This
is almost pure silica. Silica is the article required, whether it occurs
in flint or sand."
"And what do you put with it to make glass?"
"You can make glass out of two materials,-- silica
and an alkali. But it is good for nothing. It has no solidity. It will
dissolve in hot water. To give it density and hardness, we add either lime,
or-- this material."
"Red sand?" said Lawrence. "No, this is n't sand!"--
putting his hand into the barrel. "What is it?"
"Red-lead," said the Doctor.
"Ground and sifted, ready for use," added the
gaffer. "It is not ground fine, like the red-lead painters use. This
or litharge-- which is another form of almost the same substance, and
answers the same purpose-- is used in making flint glass."
"But what is red-lead? What is it made
of?"
"It is made of common lead, such as you run
bullets out of. You 've noticed, in melting it, that a thin skin always
forms on the lead, which you call
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