I am a manufacturer of steel. The steel which I make melts at a red heat, and can be

I am a manufacturer of steel. The steel which I make melts at a red heat, and can be hammered into any form. It can also be combined with other metals, so as to produce a great variety of materials. The same substance, which, when soft, is black, becomes blue when heated, and white when red-hot; and, if the heating be carried further, it melts the glass, into which it sinks. The blackest of these colours is produced by