Stonc.—The stone employed in construction at various times and places includes a number of varieties in addition to those to which particular ref erence is made. In many,' situations common building-stone serves as the principal supply for foundations. Changes in the favorite material of' different localities for fronts and entire structures occasionally occur on account of the opening of new quarries or the discovery of unexpected.de fects. Some of the latter could presumably be avoided by the exercise of g-reater care in the selection of stones from a given quarry'. A useful hint bearing on this subject may be derived from the statement that when Sir Christopher Wren built St. Paul's Cathedral lie had the stone he intended to use quarried and exposed to the weather on the sea-beach for three years before any of it was placed in the building. By similar precautions the stones taken from other quarries have been rendered serviceable for cen turies, while on account of their omission, or from other causes, the spec tacle of rapid decay or disintegration of portions of pretentious fronts is sometimes presented in this and other countries.
materials for superstructure of important buildinp-,s, 0-ranite holds a leadinc, rink In the United States several varieties have o •• • been introduced and -used in the construction of large public edifices, stores, churches, etc. On account of its hardness, special skill in dressing it is required; but such difficulties have been overcome to a great extent by the employment of skilful workmen at various places where it is quar ried and dressed or ornamented before it is sent to its final destination. Prominent varieties include the Ouincy granites, which 'have furnished the material for a large portion of the granite structures in Boston; Maine granites, embracing- red or pink, as well as varieties of other colors; New Hampshire, or Concord, granites; a granite obtained from quarries located near Richmond, Virginia, which furnished the material for several of the department buildings in Washington. Ouarries have also been opened in Rhode Island, Connecticut, Pennsylvania, Missouri, and other States.
Samistonc.—A number of varieties of sandstone, including brownstone, have been extensively used in some of the American cities as the material for the fronts of high-class dwellings and other buildings. The extensive quarrying of brownstone was commenced, and has been continued during a protracted period, in the vicinity of Portland, Connecticut. Unlike gran ite, it is usually dressed after it has reached the place where it is to be nsed. Sandstones of various qualities and colors are obtained in a number of States, including Alassachusetts, New Jersey, Pennsylvania, Maryland, Ohio, and Wisconsin. In addition to the brownstone of Connecticut, prominent varieties include bluestones of New York and Pennsylvania and Euclid blnestones and Berea grits of Ohio. Beautiful sandstones of warm
and mellow tints have been found in many of the Western States and Ter ritories.
Limestones are classified as compact, magnesian, or oolitic. In Eng land some of these varieties have been extensively used, and in the United States they have frequently furnished the material for the dwellings erected in or near limestone districts. English authorities consider that the most . important subdivision of the limestones used in masonry is the oolitic, and they place a very high estimate on one of its varieties, the Portland stout, of which superior specimens were selected for use in St. Paul's Cathedral. It is one of the few stones unaffected by the smoke of London, and this fact has greatly increased its use in that city. In the United States, Indi ana furnishes superb oolites which are extensively employed. This stone has a pleasing warm tint and is soft enough to lend itself readily to the most elaborate ornamentation.
Travertine is defined as a limestone of porous texture formed by depo sition from mineral springs. It has a warm color, may be quarried in large blocks, and is extensively used at Rome, in both ancient and modern build ings, including the Cathedral of St. Peter's.
is no substantial difference in composition and origin, in a scientific sense, between ordinary limestone and marble. The notable extent to which marble has been used in important structures, as the ex terior of the Capitol bnilding at Washington, and other exceptionally exten sive and costly edifices in the United States, is presumably due partly to the historic and artistic interest felt in the material, and partly to its inher ent beauty, its susceptibility to a high polish, the readiness with which it can be dressed or fashioned into any desired shape or form, and its attract ive varieties in color. Ouarries have been opened in Vermont, Massa chusetts, New York, Pennsylvania, Maryland, Tennessee, and Georgia, and deposits exist in a number of other States. The annual value of the native product at a comparatively recent period was abont two million dol lars, of which more than one-half was quarried in Vermont; considerable quantities are also imported, chiefly from Italy. A number of the native marbles are used princ:pally for general building, purposes, instead of deco rative work. But marbles found in East Tennessee have attracted much admiration, and have been introduced to a considerable extent since their use in portions of the interior of the Capitol at Washington. Their colors are peculiarly attractive, as they vary from light pink mottled with white through all shades to deep chocolate red, thus affording a pleasing diversity, and their texture combines closeness and compactness with nearly absolute freedom from flaws.