The igneous formation of which the greater part of the Roman Campagna is, in its superior portion, composed, contains three strata known under the common name of tufa, - the " stony," " granular," and " sandy " tufa, - the last being commonly known as pozzolana.
Lava is much used for paving-stones in the neighborhood of volcanic districts, where pozzolana (for cement) and pumice stone are also important.
The mineral wealth of the Cyclades has hitherto been much neglected; iron ore is exported from Seriphos, manganese and sulphur from Melos, and volcanic cement (pozzolana) from Santorin.
According to modern physicians it is impossible to live many days in the caves of pozzolana in which many of the catacombs are excavated."
C. i is on the earliest dwellings of man; C. 2 on systems of Thales, Heraclitus, Democritus, &c.; c. 3 on bricks; c. 4 on sand; c. 5 on lime; c. 6 on pozzolana; c. 7 on kinds of stone for building; c. 8 on methods of constructing walls in stone, brick, concrete and marble, and on the materials for stucco; c. 9 on timber, time for felling it, seasoning, &c.; and c. to on the fir trees of the Apennines.