and of a yellowish-brown colour. Of this stone the colonnade of the Piazza del Plebiscite is formed. For the more exposed and stronger kinds of masonry grey lava from the base of Vesuvius is used in Naples. Amongst the most ancient cities of Southern Italy travertine has been in use. Thus we find it occa sionally amongst the ruins of Pompeii, where it was used for corner stones and pillars to houses built of concrete. The walls and columns of Paestum, con structed of a similar material, are still in a remarkable state of preservation. From the manner in which the buildings and monuments of Italy, formed of calcareous materials, have retained to a wonderful degree the sharpness of their original sculpturing, unless disfigured by the hand of man, it is clear that a dry and smokeless atmosphere is the essential element of durability. In this respect, therefore, the humid sky and gaseous air of British towns must always place the buildings of this country at a comparative disadvantage as regards durability.
