of the principal phenomena may be best illustrated by reference to Fig. 65, an imaginary block plan, of part of an earthquake-shaken town. Whole districts at are prostrated. At both ends of the great church, and about , and along the street from to , houses have fallen, and others are grievously injured; yet these are perhaps amongst the best built and least ancient houses in the place. Passing along the main central street, after debouching over heaps of stone at , it is found, that along the greater part of its length, fissures here and there, a few chimneys, or a side wall down, as we look up some "vico," are all the signs of earthquake visible.
The great church, when examined, tells us that the horizontal direction of shock was from to . Returning now over the ground, and examining the place with the compass in hand, we find that the main street presented its length to the direction of movement; its stiff front and rere walls, its multiplied floors, have saved it. The street to , on the contrary, although of houses of the same date, height, and character, &c., is nearly destroyed; it was nearly transverse to the line of movement. The street at has escaped much better, though much injured, yet it is nearly parallel with , and the houses are as high if not higher; but we find they are some of the newest and best-built houses in the town. Some houses at the right of the Chiesa Madre are thrown down, but no others in the Piazza, have suffered. The rubbish has probably all been cleared from the Piazza in the market-place, and we cannot tell which way the houses fell, but we look at the fallen apse or campanile or transept, and find that it fell against one of these, and upon these houses. We now get out of the highways of
