said Wordsworth; but this sublime charge is committed to frail keeping.  It is itself a sepulchre of the dead; and the tragedies of the Dacian war are inscribed upon tragedies that took place long ages before there was any human eye to witness them.  The historic sculptures that so deeply move our pity for a conquered people, are based upon the immemorial sculptures of creatures whose sacrifice in whole hecatombs touches us not, because it is part of the order of the world by which life forms the foundation of and minister to life.  It is strange how many of the grandest monuments are wrought out of the creations of primeval molluscs.  The enduring pyramids themselves are formed of the nummulitic limestone studded with its “Pharaoh’s beans,” the exuviae of shell-fish that perished ages before the Nile had created Egypt.

Of the breccias there is a great variety among the relics of ancient Rome.  A breccia is a rock made up of angular pebbles or fragments of other rocks.  When the pebbles are rounded the conglomerate is a pudding-stone.  Marble breccias are formed of angular pieces of highly crystalline limestone, united together by a siliceo-calcareous cement, containing usually an admixture of a hornblendic substance, and which is due to a particular action of adjacent masses or veins of iron ore.  The hornblendic cement, with its iron or manganese base, produces the variegated appearance which may be seen in specimens from different localities.  As may be imagined from their composition, these rocks are as a rule extremely unalterable by ordinary atmospheric agencies, and are susceptible of a high degree of polish, which they retain with the utmost tenacity.  They were favourite materials with the ancient Roman decorators; but they do not occur in large masses in the city.  A beautiful pair of Roman Ionic columns under the pediment of the altar of the third chapel in the Church of Ara Coeli are made of a valuable breccia called Breccia dorata, distinguished by its small light-golden fragments on a ground of various shades of purple.  The high altar of Santa Prisca on the Aventine is supported by one column of Breccia corallina of remarkably fine quality, in which the fragments are white on a ground of light coral-red.  In the second chapel of St. Andrea della Valle there are two Corinthian columns of Breccia gialla e nera, which is an aggregate mass of yellow and black fragments:  the yellow in its brilliant golden hue surpassing that of all other marbles, and forming a striking contrast to the long irregular black fragments interspersed throughout it.  In the first chapel of the same church there are four fluted Corinthian columns of breccia gialla, containing small and regular blotches, of which the prevailing tint is orange, each fragment edged with a rim of deeper yellow that surrounds it like a shadow.  A most beautiful variety of Breccia gialla e nera forms the basin of holy water at the entrance of the Church of St. Carlo di Catinari, in which “the colours resemble a golden network spread upon a ground of black”; and an exceedingly lovely urn is seen underneath the altar in one of the chapels of the Portuguese Church, in which white fragments are imbedded in a purple ground which shines through their soft transparency.