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306 PHYSICAL AND CHEMICAL CHARACTER hardness in a stone is objectionable, as it renders it more difficult and expensive for sculpturing and moulding. In estimating, therefore, the value of hardness in the selection of a material, it must be considered whether the structure (or portion of the structure) is to be of a massive, or of an ornamental, character. 3. Structure. The structure of rocks depends chiefly upon their mode of formation. Sedimentary- rocks formed by the aqueous deposition of sand, clay, &c., over the bed of the sea, or an inland lake, have generally a laminated structure. The laminae being parallel to the planes of bedding. Laminated Structure. In placing the stone on its bed of masonry care should be taken that the planes of bedding occupy a horizontal position, and that the exposed surface is formed of a cross-section of the edges of the planes. The stone thus placed occupies in the artificial structure the position it occupied in nature, and is best protected from atmospheric disintegration. Compact. So called, when the stone presents an uniform appearance without grains or plates; such as flint, basalt, &c. Granular. When it is composed of visible grains, of greater or less size, united by a cementing ma terial ; such as many sandstones. Oolitic. When composed of a multitude of little