Looked at from the outside, there is no beauty in the cask of alum; but as soon as the interior is exposed, then the numberless crystals shooting from every part, glisten again as the light streams in upon them; and you acknowledge that the cunning by which they have been produced from the dull slaty shale is a happy triumph of chemical art--one that will stand a comparison with a recent triumph, the extraction of brilliantly white candles from the great brown peat-bogs of Ireland, or from Rangoon tar. Perhaps some readers will remember the beautiful specimen of alum crystals--an entire half-tun that stood in the nave of the Great Exhibition.
Alum is made near Glasgow from the shale of abandoned coal mines, soaked in water without burning. After the works had been carried on for some years, and the heap of refuse had spread over the neighbourhood to an inconvenient extent, it was found that on burning this waste shale, it would yield a second profitable supply of alum. Moreover, artificial alum is manufactured in considerable quantities from a mixture of clay and sulphuric acid.
In going about the works it was impossible not to be struck by the contrast between the sooty aspect of the roofs, beams, and gangways, and the whiteness of the crystal fringes in the pans, and the snowy patches here and there where the vapour had condensed. And in an outhouse wagon-loads of 'rough Epsoms' lay in a great white heap on the black floor. This rough Epsoms, or sulphate of magnesia, is the crystals thrown down by the mother-liquor after a second boiling.
In our goings to and fro, we talked of other things as well as alum; of that other mineral wealth, the ironstone, to which Cleveland owes so important a development of industry within the past fifteen years. The existence of ironstone in the district had long been known; but not till the foreman--jointly with his father--discovered a deposit near Skinningrave, and drew attention to it, was any attempt made to work it. Geologically the deposit is known as clayband ironstone; hence clay will still make known the fame of this corner of Yorkshire, as when the old couplet was current--
"Cleveland in the clay, Carry in two shoon, bring one away."
