Earllupui/ces in Sicilj/. 221 



of cutting, and the cheapness of the tufa, have caused its 

 adoption as a building-stone, contrary to the custom of our 

 ancestors, as appears from the immense excavations and pits 

 about Syracuse, Girgcnti, and some others of the ancient cities 

 of Sicily. Till lately, the common cement was composed of 

 a fat earth, to which ashes were sometimes added; it was 

 called tajo. Within a (ew years, lime and sand have been 

 used. But they do not always employ for lime that stone 

 which it hardest and most proper; nor that which requires 

 an equal degree of heat in calcination ; nor are all the pieces 

 white. It is not slaked methodically, nor mingled with that 

 patience which caused the ancients to say, that lime should 

 be tempered by the sweat of the brow. And here, indeed, 

 this labour is the more indispensable, as Palermo is destitute 

 of puzzolana, and of those ferruginous earths, which render 

 such valuable service to those volcanic towns of the island, 

 which can obtain a cement so adhesive and durable. 



The soft rock of the surface serves, in large masses, for 

 a foundation upon the clay. But the brittleness of the rock, 

 and the instability of the earth, its readiness to change from a 

 level at the least motion, or by the action of moisture, which 

 the air and soil of Palermo make permanent, render the 

 foundation very far from firm. 1 have seen pieces of the 

 foundation of large edifices, so entirely reduced to earth, as 

 to be removed with a spade. This inconvenience exists even 

 when the rock in its natural situation serves as the base. 

 Where a building is raised upon a soil, the parts of which 

 are of different natures, it must suffer much from the unequal 

 resistance of this soil. The right side of the royal palace, 

 has for several years been inclining from a perpendicular, in 

 consequence of its having been placed on the ancient allu- 

 vial formation, while the remainder of the building rests on a 

 rock. Sometimes we see buildings raised on an inclined 

 plane, with one part of the base more elevated than the 

 other; in this case, it is evident that the oblique pressure 

 is compounded of two forces ; one, perpendicular to the 

 resistance, and which is overcome by it; the other parallel 

 with the resistance, but which, not entering into the action, 

 operates in its own direction. The equilibrium is thus de- 

 stroyed, and the stability of such buildings cannot be of long 

 duration. 



