Quotation from: General ScienceWritten by: Bertha M. Clark |
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But while most substances have a definite melting point, some substances do not. If a glass rod is held in a Bunsen burner, it will gradually grow softer and softer, and finally a drop of molten glass will fall from the end of the rod into the fire. The glass did not suddenly become a liquid at a definite temperature; instead it softened gradually, and then melted. While glass is in the soft, yielding, pliable state, it is molded into dishes, bottles, and other useful objects, such as lamp shades, globes, etc. (Fig. 20). If glass melted at a definite temperature, it could not be molded in this way. Iron acts in a similar manner, and because of this property the blacksmith can shape his horseshoes, and the workman can make his engines and other articles of daily service to man.
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