Among the applications of iron to decorations of civil architecture must be specially mentioned the nails and knockers on the doors of houses, which are so characteristic of Toledo and other old Spanish towns. This style was imitated from the Moors. Some doors still exist at the Alhambra, Granada, covered with enormous heads of nails of a half-spherical form with embossed pattern. These same nails are constantly to be found on old Spanish houses, to which are added in the angles pieces of iron of a most artistic order. A large number of these nails from Toledo, are in the Kensington Museum. Examples of two are given. [Illustration: SPANISH NAIL HEADS. SOUTH KENSINGTON MUSEUM.] After the 16th century this industry loses its artistic interest and importance. Ironwork becomes simply practical and useful, and ceases to reproduce the grand carved and chiselled works of former times. The artistic objects are reduced to specimens on a small scale: door-locks, of which an excellent example exists at the church of Calatravas, Madrid; a weighing machine, made by the locksmith Salinas for the Mint in the 17th century, which was exhibited at the Special Loan Collection of Scientific Apparatus at Kensington in 1876, the fine ornamentation of the clock of the cathedral of Seville, made in the last century by Friar Josef Cordero, and the very remarkable iron locks made by Millan at the beginning of the present century, for the rooms at the palace of the Escurial, called "Piezas de Maderas finas." The art of inlaying iron with gold and silver, constitutes in Spain a special industry; the principal artists who carry it out at the present time with great skill are Messrs. Zuluaga at Madrid, and Alvarez at Toledo. The splendid sepulchre of General Prim at the church of Atocha, Madrid, made entirely of damasquiné ironwork, is worthy of the greatest commendation; the fine vases and shields of _repoussé_ ironwork inlaid with gold, made by Alvarez of Toledo, are artistic and excellent revivals of the Milanese work of the 16th century. IRON MASTERS. Year in which Locality of they worked. Name. their Residence. 1520. Avila, Fr. Juan de Guadalupe. 1527. Andino, Pedro Seville. 1540. Andino, Christoval Toledo. 1557. Arenas, Hernando Cuenca. 1523. Bartolmé, El Maestro Jaen and Seville. 1555. Barco, Alonso Palencia. 1559. Brabo, Hernando Toledo. 1579. Cela, Juan Tomas Zaragoza. 1541. Cespédes, Domingo de Burgos. 1561. Corral, Ruy Diaz del Toledo.