"What is the effect of using an alkali with the quartz sand?"
"Quartz possesses all the qualities of an acid, so that when the alkali is fused with the quartz a neutral substance, unlike either, is formed."
"What kind of alkali is best to use?"
"That depends on what it is to be used for. Quartz and lime make a fine window glass product. Bottle glass is usually made of soda and quartz; window glass is also made of quartz, soda and lime; plate glass of quartz, lime, soda and potash; and flint glass has only the alkalis, potash and oxide of lead."
"Well, for our purposes, wouldn't it be better to make the glass out of quartz and lime if windows can be made out of it?"
"By all means, for several reasons: We have the lime on hand, and also because it makes a very hard article."
"What can we melt it up in?"
"The clay retort or crucible will just be the thing for the purpose, and the first thing in the morning I will make a tour to a point close at hand, where I think we shall be able to get a good quality."
The boys were astir in the morning earlier than usual. They had a new impulse—something to learn and to do. Harry busied himself with putting the crucible in order, and in getting the fuel. George, after his usual morning's work, brought in the lime, and broke it up preparatory to grinding it up into small particles, so that it would intimately mix with the sand.
Within an hour the Professor returned with several samples of sand, either of which, he thought, would make a good article. The yaks were hitched up, and George went with him to get a good supply.