Frequent specimens of a beautiful marble known as _Fior di Persico_, from the resemblance of the colour of its bright purple veins on a white ground to that of the blossom of the peach, may be found in the Roman churches. It was much used for mouldings, sheathings, and pedestals, and also for floors. In the Villa of Hadrian large fragments of slabs of this marble may be found, which lined the walls and floors of what are called the Greek and Latin Libraries. The Portuguese Church in Rome has several columns of Fior di Persico supporting the pediments of altars in the different chapels; especially four pairs of fluted ones which adorn the two altars at the extremity of the nave, which are among the largest and finest in Rome. But the most splendid specimens of all are a pair of columns in the Palazzo Rospigliosi. The dado, eight feet in height, in the gorgeous Corsini chapel in the Church of St. John Lateran, is formed of large tablets of highly-polished Fior di Persico, and the frieze that surrounds the whole chapel is composed of the same beautiful material, whose predominance over every other marble is the peculiarity of this sanctuary. The ancient name of this marble was _Marmor Molossium_, from a region in Epirus--now Albania--which was a Roman province in the time of Pompey. It is associated with the celebrated campaigns in Italy of Pyrrhus, king of Epirus, in which Greece was for the first time brought into contact with Rome. The region in which the quarries existed was the most ancient seat of Pelasgic religion. The infinite hues and markings of the coloured marbles have all been painted by Nature with one material only, variously proportioned and applied--the oxide of iron. The varieties of marble are mainly caused by the different degrees in which this substance has pervaded them. They are variable mixtures of the metamorphous carbonates of protoxide of iron and lime. And it is an interesting fact that there is a distinct relation between deposits of magnetic iron ore and the metamorphoses of limestones into marbles; so that this substance not only gives to the marbles their colouring, but also their texture. Even the whitest saccharoidal or statuary marble, which it has not coloured, it has created by the crystallisation of the limestone associated with it. And the marbles of the entire province of the Apuan Alps owe their existence to the large quantities of iron ore disseminated throughout them, which have exercised a great influence on the molecular modification they have undergone. The same changes have been produced on the limestones of Greece and Asia Minor by veins containing iron ore running through them.