Its industries include the manufacture of tiles, pasteboard wares and gardening implements, while there are coal mines in the vicinity.
After copies of such reliefs have been taken in gypsum, cement, statuary pasteboard, fossil dust mixed with vegetable oil, or some other suitable material, they are painted.
A matrix of wood or iron is covered with successive layers of papers, pasted together so as to form pasteboard.
But, if the pasteboard be interposed so as to intercept the vibrating segments AOB, DOC, the note becomes much more distinct.
The reason of this is, that the segments of the plate AOD, BOC always vibrate in the same direction, but oppo sitely to the segments AOB, DOC. Hence, when the pasteboard is in its place, there are two waves of same phase starting from the two former segments, and reaching the ear after equal distances of transmission through the air, are again in the same phase, and produce on the ear a conjunct impression.