Great Neapolitan Earthquake of 1857/Part I. Ch. III
CHAPTER III.
CONDITIONS OF EARTHQUAKE ACTION UPON ARCHITECTURAL STRUCTURES.
The effects produced by precisely the same shock, acting upon buildings differing in position, construction, material, &c., are so great, that it will be necessary to treat somewhat in detail of the conditions of earthquake action upon architectural structures; for without a thorough understanding of these, one is almost certain to be led astray by the strange, and often, at first sight, perplexing phenomena of destruction observable.
Throughout the kingdom of Naples, the edifices of cities, towns, and rural places present very uniform and striking characteristics, though varying much in dignity and size, &c.
In a few of the largest provincial cities, such as Potenza, Melfi, (No. 10, Coll. Roy. Soc.,) &c., the buildings, more especially those of government, the ecclesiastics, and the great landowners, present more or less of the majestic size, and architectural style, of the city of Naples itself. Loftiness, thickness of walls, apertures few but large, square-headed windows, and arched doors and gateways, with heavy tiled roofs, of low pitch, and with deeply overhanging eaves characterize the outside. The style of architecture, when style is attempted, is generally Roman, with cinque cento, or a still later and more debased style of ornamentation. The usually grandiose effect, however, very generally conceals, building workmanship of a very inferior quality.
The building materials of the kingdom generally, are lavas and tufa in the volcanic districts, limestone of various qualities, and brick (these are by far the most prevalent); and, in their respective localities, some sandstones, slaty rocks, and very rarely those from the ancient igneous rocks.
Limestone and brick are the staple materials of the regions to which this Report principally refers, except those of Naples and Melfi. The limestone is very seldom found, either in the jurassic or cretaceous formations, well bedded, or capable of being raised in long flat blocks. Lime is abundant, but the mortar often of very slender cohesion, from too great a proportion of lime and the want of a proper quality of sharp sand. Hence the general style of construction of wall, even in first-class buildings, consists of a coarse, short-bedded, ill-laid rubble masonry, with great thickness of mortar joints, very thick walls, without any attention to thorough bonding whatever. The opes of windows and doors often have cut limestone jambs, lintels, and dressings, which are but ill connected with the rest of the walls. In general, the external faces of the walls are concealed by plaster or rough east. This is even the usual style of building for the better class of churches and monasteries. It has prevailed from a remote period, and a fair average illustration of its appearance is seen in the west end of the Villa Carasso near Auletta (No. 11, Coll. Roy. Soc.). The floors in the better sort of town houses and palazzi, are formed of joists of fir timber, very commonly round as it grew, from 6 to 9 inches in diameter, placed at about 3 feet apart. The ends are inserted some inches into the walls, but are neither bedded on, nor connected by, any "tossils" or bond timbers, none of which are ever placed in the walls. Upon these joists a planking of fir, oak, or chestnut, from an inch to an inch and a half thick, is laid, rough as it comes from the saw, and pegged or spiked to the beams, and upon it a bed of concrete or beton, composed of lime, mortar, and broken tufa, brick, or stone is laid, to 6 to 8 inches in depth, and the surface of the latter is laid with red tiles—square or hexagonal—or sometimes plastered over with puzzolano mortar, and painted in oil.
The under surface of the floor is often bare, and the joists visible; in other cases a plastered ceiling is secured, by heavy lathing, up to the joists. See Photog. No. 12 at St. Pietro (Coll. Roy. Soc.)
A floor of this sort weighs from 60 to 100 lbs. to the superficial foot. Floors of palazzi, are also not unusually formed of arches and groins, built of hollow pottery embedded in mortar, the haunches filled in with beton, and plastered soffeits, with tiled surfaces to the floors, which, thus constructed, are of still greater weight.
The roofing also usually consists of round fir timber. The framing is of the simplest character except in some church and other roofs of great span, when the timber is squared. It consists commonly of principal rafters at 3 to 5 feet apart, connected by a rude collar brace, of round fir also, trenailed or bolted to the rafters. The feet of the rafters sometimes rest upon a wall plate of squared or of half-round timber, but often bed directly on top of the wall. These principals are crossed by stout sawed laths, and upon these are laid the common heavy ridge and furrow tiles, whose appearance is so familiarly characteristic of Italy, and so much more picturesque, than constructively good. These tiles are from ¾ to 1¼ inch thick, each course from 18 to 24 inches long, and they are frequently laid dry, and not secured down in any way but by their own great weight, except at the ridges, where the ridge tiles are cemented down in mortar. Roofing of this character weighs very little less than an equal surface of the flooring just described.
Framed roofing of large span and squared timber is not common in churches, &c., which are usually vaulted with brick or stone, dome'd or groined.
It will thus be remarked that in the construction of the more important buildings, the mass and inertia, of walls, floors, and roofs are enormous, while the bond and connection of each of these, and of all to the others, is loose and imperfect.
It is in the medieval towns and villages of the interior provinces, however, that these conditions are still more evident. Nothing can be more striking than the general appearance of these ancient abodes. They are almost without exception perched upon the summits and steep flanks of precipitous "collines," usually rounded conoidal hills of limestone, sometimes abrupt and rocky elevations, whose slopes and shelves are occupied and their craggy heights crowned by the houses, built out to the very edge of the precipice, with no windows or doors looking outwards, or, if any, high up and inaccessible to any Photo Pl. 13
Castelluccio.
valley bottom, through the keen bright air, and relieved against the sky, these old towns seem as though we could reach their interior in half an hour's scramble; yet often three hours' painful toil upon our mule will but suffice to bring us—by long traverses over rough and rolling stones, and by an approach road that is often the bed of a torrent in time of rain—to the ancient gateway, or to the narrow and obstructed street entrance by which alone we can penetrate the interior. Everything about these places is characteristic of their origin, its remoteness, and of the savage manners and times in which they were founded.
The irregular and narrow streets, not more than from 5 to 12 or 15 feet wide, are steep as staircases, until we reach the very summit of the town, where the little "piazza" and the principal church, or some gloomy-looking monastic pile, mostly form its centre and heart. We pass along between houses of all heights and sizes, beetle browed, and with low arched "portone," and small, unglazed, and often sashless windows, few, and high up. The unpaved and unformed surface, often the bare rock worn into steps, of these wretched streets, is the common receptacle of the filth of every house; pigs at all times, and often goats at night, make them their common resting-ground. There is neither sewerage nor water supply, and in winter wet, we wade through ordure ankle deep. Castelluccio (see Photog. 13) is a good illustration of the site and exterior of many of these towns. They all still retain the impress, of the semi-oriental character of the early settlers of Magna Græcia, of the savage violence and tyranny, of Saracen and Lombard conquerors, of middle-age superstitions and barbarism, and of a people condemned for ages, by misgovernment to an unprogressive state of ignorance and poverty, in the midst of the richest bounties of nature.
The towns owe their elevated position, primarily beyond doubt, to the necessity for defence and security in ancient times; but an universal belief exists that this elevation secures them against malaria, as it certainly relieves them in the summer from the unbearable reflected heat and pent-up air of the valley bottoms. These advantages, however, seem dearly purchased at the cost of difficult accessibility, even were proper road approaches made to them.
No roads whatever, suited to wheel traffic, exist throughout the kingdom, except the five great military ways, and these are perfectly unconnected by branches, with any but a few great towns: hence all produce has to be carried by mules, or by hand; and journeying off the military road can only be accomplished in the same way, or on foot.
It results from the perched positions, of almost all these towns that they are exposed to the severest effects of every earthquake shock. They are rocked as on the tops of masts. Padula is a good example of the larger and less ancient class of these towns (Photog. 14).
The style of building in these provincial towns, is much the same as has been already described of the cities, but poorer and humbler. The houses are seldom under two stories, rarely exceed three. The huts of the poorest classes (the land labourers and shepherds) are but one story, huddled together in utter confusion; and the chief difference in point of masonry, in these country towns 
Padula.
from that described is, that surface limestone—or that taken from the naturally exposed beds of rock—is commonly used to save labour in obtaining better, and hence the walls built almost invariably, of this coarse "nobbly" rubble, in half-rounded blocks, or rather lumps. of stone, of nearly equal length, breadth, and thickness, and resembling nothing in form more than irregular loaves of bread, are almost devoid of masonry bend, and are shaken down into a heap, by a shock that would only fissure a well-built and properly bonded structure.
It results, too, from the extreme steepness of the scarps and terraces upon which these poor edifices are placed, that when some are shaken down they fall against and upon those that are beneath them, and increase thus the common ruin. This took place with dreadful effect at Saponara and elsewhere in the shock of 16th December, 1857.
The hill sites of these provincial towns are found most commonly on the summits and flanks of the lower spurs of hills that skirt the great mountain ranges, and are on the confines of the "piani," or great valley plains or slopes, that separate the chains; but sometimes they are absolutely upon lofty mountain tops (Contarso, Montesano), or at the edges of steep ravines (Bella); or on spurs high up on mountain flanks, as Petina, on the flank of La Scorza. Occasionally they stand (or stood) upon the fiat tops, of insulated and enormously deep masses, of loose alluvium and clay, like Montemurro and Sarconi, with large rivers or torrents running at the bases of the clay cliffs, and eating them away.
This is almost universally the case in the great piano of Calabria Ulteriore Primo, and hence the expression of Dolomieu, as to the destruction of the towns there in the great shock of 1783, that "the ground was shaken down like ashes, or sand laid upon a table."
Further remarks as to the situation of these towns, however, will best be made when observing upon some of the great physical features of the earthquake region, and of Naples generally.
With these remarks as to the general character of the buildings we have to deal with, I now proceed to the consideration in detail of the effects of earthquake upon them, and the phenomena presented by fractures and fissures in their walls, floors, &c. &c.