« PreviousContinue »
was iu later times represented as descended from Aeneas, and Sabines to attend them with their daughters. In the while others, preserving the legend more in its original midst of the solemnities the females were forcibly carried purity, made no mention of its Trojan descent. The main off: the number thus taken was said to have been thirty. features of the Roman legend which are preserved in Livy The three nearest Latin towns, Antemnæ, Cænina, and (i. 3, &c.; Cio., De Republ., ii. 5; comp. Plut., Romul., 3, Crustumerium, now took up arms against Rome, but Ro&c.; Dionys. Hal., i, p. 61, &c.), are these :
mulus defeated them successively, and having slain Acron, When Procas, king of Alba, died, he left two sons, Nu- king of Cænina, he dedicated the first spolia opima to mitor and Amulius. The latter wrested the government Jupiter Feretrius. The Sabines, under their king Titus from his elder brother, who yielded without a struggle, and Tatius, likewise made war upon Rome, and the treachery of lived as a private person in quiet retirement. But Amulius, Tarpeia, a Roman woman, opened to them the gates of fearing that the descendants of his brother might punish the fortress on the Capitol. The Sabines attempted to him for his usurpation, had the son of Numitor murdered, storm the city, and Romulus in this emergency vowed a and made his daughter Silvia a priestess of Vesta, an office temple to Jupiter Stator, in order to inspire his men with which obliged her to perpetual celibacy. One day however courage and to prevent them from flying before the enemy. when Silvia went into the sacred grove to draw water from The war was continued with doubiful success, and finally the well for the service of Vesta, an eclipse of the sun took terminated by the Sabine women throwing themselves beplace, and the maid, frightened by the appearance of a wolf, tween the combatants, and thus restoring peace between Hled into a cave. Here she was overpowered by Mars, who their fathers and husbands. Romulus rewarded the women promised her a glorious offspring. She was delivered of of Rome for their services by the grant of various privileges, iwins, but the god apparently forsook her, for she was con and the thirty curiæ were called after the names of the demned and put to death by Amulius, and it was deter-thirty Sabine women. The two nations, the Romans on the mined that the two children should be drowned in the Palatine, and the Sabines on the Capitoline and the Quiriver Anio. But the river carried the cradle, with the rinal, were united as one nation, though each continued to children in it, into the Tiber, which at the time had over have its own king. flowed its banks. The cradle was driven into shallow The two kings and the citizens of the two states met in water to a wild fig-tree (Ficus Ruminalis) at the foot of the the valley between the Capitoline and Palatine (comitium) Palatine hill. A she-wolf, which came to the water to drink, whenever it was necessary to transact business which was heard the cries of the children, and suckled them, whilst a of importance to both nations. This union however did not woodpecker, which was, like the wolf, an animal sacred to last long, for Tatius was killed during a national sacrifice at Mars, brought them other food whenever they wanted it. | Lavinium, and Romulus henceforth ruled alone over the This marvellous spectacle was observed by Faustulus, the two nations. herdsman of the flocks of king Amulius, and he took the During the period that Romulus was sole king, he is saia children and carried them to his wife Acca Laurentia or to have carried on two wars, one against Fidenae, and anLupa. Thus they grew up in the shepherd's straw huts on other against Veii. Fidenæ commenced the war from fear the Palatine; that in which Romulus was said to have lived of the growing strength of its neighbour; but Romulus got was kept up to the time of the emperor Nero. The two a victory over them by stratagem, and took possession of youths became the stoutest and bravest among their com- their town. The war against Veii rose out of that against rades, with whom they shared their booty. The followers Fidenæ, for both were Etruscan towns. Veii was likewise of Romulus were called Quinctilii, and those of Remus, humbled, but it obtained a truce of one hundred years, after Fabii. A quarrel one day broke out between the two surrendering part of its territory to Rome. brothers and the shepherds of the wealthy Numitor. Remus Such are the fortunes and achievements which the old was taken by a stratagem, and led to Alba before Numitor, Roman legend ascribed to the founder of the city. Respectwho, struck by his appearance and the circumstance of the ing his political institutions, see the article Rome. He is age of the two brothers, ordered Romulus likewise to be said to have died after a reign of thirty-seven years (716 brought before him. Faustulus now disclosed to the young B.C.). His death is represented in as marvellous a light as men the secret of their birth, and with the assistance of the his birth. On the nones of Quinctilis, or on the Quirinalia, faithful comrades who had accompanied them to Alba, they the king, while reviewing his people near the marsh of slew Amulius, and their grandfather Numitor was restored Capra, was taken up by his father Mars, and carried to to the government of Alba.
heaven. The people in terror fled from the spot; but The love of their humble home however drew the youths Romulus soon afterwards appeared as a glorified hero to back to the banks of the Tiber, to found a new city. The Proculus Julius, and bade him inform his people that in district assigned to them for this purpose by Numitor ex. future he would watch over them as the god Quirinus. tended in the direction of Alba as far as the sixth milestone, Such are the main features of the story of the founder of which was the frontier of the original Ager Romanus, and Rome, which was handed down by tradition, and commewhere, down to a very late period, the Ambarvalia were morated in national songs to the time of Dionysius. (Dionys, solemnized. A dispute arising between the brothers as to Hal., i., p. 66.) Writers both antient and modern havo the site and name of the new city, it was agreed that it attempted to elicit historical truth from this beautiful and should be decided by augury. Romulus took his station on in most parts truly poetical legend, or have struck out some the Palatine, and Remus on the Aventine. Remus had parts of the narrative as altogether fabulous, and retained the first augury, and saw six vultures, but Romulus saw others which are more in accordance with the events of real twelve. Considering that his double number was a signal history. The mischievous results of such perverse criticism proof of the favour of the gods, Romulus and his party have been clearly shown by Niebuhr (i., p. 235, &c.). The claimed the victory. In observance of the rites customary acts and institutions attributed to Romulus which are of among the Etruscans in the building of towns, Romulus any importance to the historian, and which from their yoked a bullock and a heifer to a plough and drew a furrow connection with events of a more historical age, or with the round the foot of the Palatine hill to mark the course of the general state of the nations of Italy, may be considered as walls and of the pomerium. Over the parts where he in- history, are given in the article Rome. tended to build the gates (portæ), he carried (portare) the RONCESVALLES (French, Roncevaux) is the name plough. The new city thus built on the Palatine was of a valley formed by the Pyrenees of Navarre between called Roma. Remus, who felt indignant at the wrong Pampeluna and St. Jean Pie de Port, on the French fronwhich he had suffered, in order to show his contempt of the tier. It is also the name of a small village in that valley, rude and simple fortifications, leaped over them; and Ro- remarkable only for an antient abbey (Nuestra Señora de mulus punished his brother's insolence by putting him to Roncesvalles), where the tomb of Don Sanchu el Fuerte death.
(the strong), king of Navarre, is shown, as well as several The population of the new city being very small, the antient relics bearing the name of Ro.and. According to gates were thrown open to strangers. Exiles, robbers, run- tradition, this hero, and many others of Charlemagne's away slaves, and criminals flocked to the city as an asylum, peers, who had invaded Spain in 778, whilst attempting and found a welcome reception. The only thing they now to regain France, were surrounded by the Navarrese, comwanted was women; but none of the neighbouring people manded by Bernardo del Carpio, and put to death. This were willing to form matrimonial connections with the new event however, which forms the subject of many Spanish settlers. Romulus therefore had recourse to a stratagem; romances and chivalrous chronicles, is far from being supbe proclaimed that festive solemnities and games should be ported by historical evidence. held in the city, and he invited his neighbours the Latins RONDA, a city in the south of Spain, formerly belonging
to the province of Malaga, is now the capital of a province | Pasquier, and others commended him highly; but modem
i to called since the late division of the Spanish territory. critics have judged him more severely. Boileau says that It is generally supposed, though erroneously, to occupy the Ronsard's language was a heterogeneous compound of vasite of the antient Arunda (Plin., iii. I), which stood some rious languages and dialects, and that his muse spoke Greek miles to the south-west. It is an ascertained fact that it and Latin in French verses. Malherbe and La Bruyère was entirely built by the Moors, with the remains of Aci- bave spoken of him in the same strain. Charles IX. benippo, or Ronda la Vieja (old Ronda), which is two leagues stowed on Ronsard an abbacy and other benefices. His to the north, and where the ruins of an amphitheatre, a moral conduct however is said not to have been strictly cletemple, aqueduct, and extensive walls are still standing. rical. He died in 1585, in one of his livings near Tours, Ronda is situated in the midst of the lofty mountains of the and a solemn funeral service was celebrated in honour of Sierra de Ronda, and is fourteen leagues from Gibraltar, him at Paris, in the chapel of the college of Boncour. Rontwenty from Cadiz, and about the same distance from Seville. sard had certainly poetical genius, but he was deficient in It is considerably elevated above the sea, being built on a taste. He was in inis respect in France what the seicenhill, which terminates abruptly just below it to the west. tisti of the following cencury were in Italy and Spain. His The city is separated into two parts by a very narrow ravine poetical works are numerous; they consist of odes, bymns, of great depih, called El Tajo (ihe cui), through which flows eclogues, &c. . * Mascarades, Combats, et Cartels faits à Paris the river Guadiaro. Though divided by nature, the city has et au Carnaval de Fontainebleau.' He also began a poem, La ! been united by means of a bridge of most stupendous dimen- Franciade,' which he left unfinished. His works are now sions, springing from the banks of the river on massive stone nearly forgotten. The most complete edition of them is that piers, and at tre height of nearly 400 feet above the bed of by Richelet, 2 vols. fol., Paris, 1623. the river.
ROOD, the quarter of an acre. [ACRE.] The city of Ronda has a population of about 20,000 inha ROOF, the covering of a house or other building. The bitants. The streets are narrow, but clean. There is a name, in its most extended sense, embraces the external public walk, called Alameda, well shaded with trees and covering itself, and the framework by which it is supported; shrubs; and a Plaza de Toros (bull-ring), built entirely of but, as a term in carpentry, it is limited to the carcass roof stone, and capable of holding eight or nine thousand per- or framing. sons. The Alcazar, or Moorish castle, one of the most ex The importance of this part of a building can hardly be tensive and best built in all Andalusia, is now a mass of overrated, since on its right construction depends not only ruins, having been blown up by the French on their eva the comfort of those for whose shelter it is designed, but also cuation of Ronda during the Peninsular war. It was con- the safety and durability of the edifice itself. For the sidered impregnable as long as the Moors held it, and re former of these purposes it is desirable that a roof should sisted several sieges, until it was finally reduced by Ferdi- exclude extremes of heat and cold, and be impervious to nand in 1485, towards the close of the Moorish war. [MOORs.] rain or snow. For the latter, the exclusion of water is With the exception of a few tan-yards, which are not in a equally necessary, and it is essential that the framework be very prosperous condition, Ronda bas no trade whatever; so disposed as to throw the least possible strain on the walls. the inhabitants occupy themselves chietly in farming and By a judicious arrangement in this particular, a roof may not raising fruits and vegetables for the consumption of Gibral- only be prevented from pressing on the walls in an injutar. An annual fair, originally instituted for the sale of rious manner, but may be made to contribute greatly to the horses, but which now is not confined to that traffic, is held stability of the whole structure. In order to the due como at Ronda. It is attended by merchants from almost every bination of the requisite qualities, an intimate acquaintpart of southern Spain.
ance with the principles of mechanical philosophy is indisRONDEAU (Fr.), or RONDO (It.), a kind of air con pensable; and a correct knowledge of the strength of í sisting of two or more strains, in which, after finishing the different materials, when exposed to various kinds of second strain, the first is repeated, and again after the third, strain, is necessary to the economical adjustment of the &c., always returning to and concluding with the first. dimensions of the several parts of a roof. A roof of large (Rousseau.)
span forms, indeed, one of the most interesting appliRONDELE'TIA, a genus of plants of the natural family cations of the science of carpentry, theoretical or cou: of Rubiaceæ, named after Rondelet, a French botanist of structive. the sixteenth century. It is characterised by having a In order to cover in a building in which the space to be calyx with a subglobular tube. Corol superior, funnel- spanned is greater than can be covered by single blocks of shaped, ventricose at the throat. Segments four to five, stone extending from one point of support to anotber, it is ovaie, obtuse, spreading. Anthers four to five, sessile within necessary either to have recourse to the principle of the ! the corol. Ovary two-celled. Style filiform. Stigma bifid. arch, as in vaults and domes of stone or brick, or to form a Capsule round, crowned with the limb of the calyx. Seeds framework of timber to support the covering. The former minute, numerous, or few when abortive. The genus, as plan is objectionable in the case of ordinary buildings from formerly constituted, included many shrubby trees which its expense and weight, and from the great solidity required occur in India (Roxb., Fl. Indica), but these have been re in the walls, where they have to be used as the abutments ferred by modern botanists to Adenosacme, Greenia, and of an arch. The principles on which such coverings of ms. Wendlandia. The present genus Rondeletia occurs chietly sonry are formed are explained under ARCH and DONE, and in America and the West Indies.
in this article the more usual kind of roof, that sustained RÖNGEBIRGE. (GERMANY.]
by a wooden framing, will be described. Such structures RONSA'RD, PIERRE DE, born in 1524, in the dis occasionally partake of the character of an arch or dome, trict of old France called Vendômois, was the son of a but more usually consist of Hat planes variously disposed. maître-d’hôtel of Francis I., who made him a knight. Roofs formed of one level plane, which are extensively used Pierre studied for a short time in the college of Navarre at | in eastern countries, are not adapted for buildings in which Paris, but soon after he entered the service of the duke of a large space has to be spanned over, nor to resist the pene Orléans, son of Francis I., in the quality of page. He after-tration of water; and are therefore unsuitable for climates wards attended, in the same capacity, James Stuart, king of in which rain and snow are common. A simple inclined Scotland, who had come to Paris to marry Marie de Lor- plane is well adapted to resist injury from weacher, but, as raine, and he accompanied James on his return to Scotland, it is scarcely more favourable to an economical disposition where he remained three years. On his return to France of the timbers than a Hat roof, it is only suited for small he resumed his post with the duke of Orléans, who sent him buildings, and is seldom vised except as a lean-to. Another on several missions to Scotland, Ireland, and other countries. objection to its use on a large scale is the disproportionate He was afterwards sent by Francis I. on a mission to Pied-height it requires in one side of the building. The best mont. In these several journeys he suffered much, in con- figure for a simple roof is that formed of two inclined planes, sequence of which he became deaf. On withdrawing from rising from the two opposite walls that approach nearest lo active life he retired to the college of Coqueret, where he each other, and meeting over the centre of the edifice, so as ; studied the classics under Turnèbe, became a good to form a ridge. By this form, supposing the same slope to Greek scholar, and took orders as a priest. He also began be maintained, one half of the height of ihe single included writing French poems, and was crowned in the floral games plane is avoided ; and, the length of the timbers being at Toulouse. [CLEMENCE, Isaure.] He was considered as diminished one half, their scantling may be considerably the successor of Marot, and the chief of the French poets of reduced. Fig. 1 represents a plan, with side and end views the tinie. [Marot.) Montaigne, De Thou, Scaliger, Muret, of such a roof, which is called a common or gable-ended roof
tween roofs with dripping eaves, and those in which the
water is collected in gutters. In the former case the roof End.
projects several inches, or even feet, beyond the walls, and the water running from the roof either drops at once on the ground, or is collected in troughs fixed under the margin of the eaves, and conducted by them to descending pipes.
This arrangement has a clumsy appearance, and is perhaps Frequently four inclined planes are used, disposed as shown eaves, though it is essential to the dryness of the walls when
unnecessary where a sufficient projection is given to the in fig. 2, representing a hipped roof, which takes its name they are of the diminutive size ofien adopted by modern from the hips, or inclined ridges formed by the meeting of builders. In gutter roofs the timbers do not extend to the Fig. 2.
outside of the walls, which are carried up as parapets, of a
reduced thickness, to such a height as to conceal the roof End.
either wholly or partially. The gutters, which are troughs of wood covered with lead or oiher metal, are laid at ihe bottom of the slopes, just within the parapets, and have a gentle inclination (usually about an inch in ten feet), to
cause water to run freely towards the pipes. In extensive the sides and ends. Where a hipped roof covers a perfectly the elevated end of the gutter may cover as little of the roof
roofs it is well to use two or more falls instead of one, that square building, the faces all meet in a point, and form a pyramid; but when, as in the diagram, the plan of the roof as need be. Similar troughs are often used in the valleys. is oblong, the planes rising from the nearest opposite walls Gutters are generally made wide enough for a man to walk meet in a ridge. Sometimes the inclined faces are not con
along them, and should be sufficiently capacious to avoid all tinued upwards till they meet
, but the roof is completed by risk of overflowing during a sudden heavy fall of rain. a horizontal plane. Such a roof is called a truncated,
The degree of slope given to the inclined faces of a roof terrace, or cut roof, and may have two, three, or four in varies according to the covering material employed, as well clined faces. Fig. 3 represents a truncated roof hipped at as to the climate. The antient Grecian temples had very one end, and terminating at the other in a vertical wall, low, or pediment roofs, varying from about 120 to about 160, like the gable-ended roof.
the height being from one-ninth to one-seventh of the span.
In Roman buildings the inclination is somewhat greater, Fig. 3.
being usually 23° or 24°, or from one-fifth to two-ninths of the span. The general introduction of the pointed style of architecture led to the use of very high-pitched roofs, a very common proportion being that in which the length of the rafters is the same as the span, so that they formed an equilateral triangle. In comparatively modern domestic archi
tecture in this country, it has been considered desirable for This arrangement is useful in diminishing the height of a and an angle of 45° is still considered by some to be the best
the length of the rafters to be three-fourths that of the span, roof, the level platform being covered with lead to compensate for the want of slope. It should be observed however pitch when plain tiles are used. As builders can, in the that even this part is not perfectly level, the centre being present day, obtain excellent covering materials
, the pitch slightly elevated to throw off water. A similar saving of may be made of any required degree, down to the low height is frequently obtained by means of a roof in which architecture and the taste of the builder; the most common
Grecian pediment, and it therefore depends on the style of each sloping face consists of two planes of different degrees of height being from one-fourth to one-third of the span, inclination. This form, which is denominated a curb roof High roofs discharge rain the most rapidly, and
do not res; (or, from its inventor, a Mansarde roof), is very common in tain snow so much as those of low pitch ; but where they London, because it affords more space for the formation of have gutters they are liable to become choked by snow bedrooms in the roof than the simpler forms. A curb roof Sliding into them, and to overflow from water running into may be hipped or not, according to circumstances. Fig. 4 them faster than the pipes can convey it away. Steep roofs represents it hipped at one end only, as the last figure, showing, like the previous diagrams, the plan, and side and end may be covered with small slates, and are less likely to be elevations.
stripped by violent winds. Low roofs, in consequence of Fig. 4.
their superior lightness, are less expensive, the timbers not only being shorter, but of proportionately smaller scantling, and they press less injuriously on the walls. The following table, extracted from Tredgold's Elementary Principles of Carpentry,' shows the proper angle for roofs covered with the materials specified in ihe first column, the last column indicating the comparative weight of each kind of covering :
Height ofruof Weight upon a Such are the principal forms of roof used in covering
in parts of simple rectangular buildings, but they require many modi
roofing. fications 10 suit irregularities of shape, or combinations of Copper or lead ... 3° 50' rectangular forms. Thus in Figs. 5 and 6, which represent
lead... 700 the junction of different roofs or portions of roofing at right Slates, large
1120 angles with each other, the lines aaa indicate valleys, Ditto, ordinary 26° 33'
900 to 500 Stone slate 29° 41'
2380 Plain tiles ..... 29° 41'
1780 Fig. 5. Fig. 6. Pan-tiles,
650 Thatch of straw,
reeds, or heath..
In describing the timber-work of an ordinary roof, each of the planes of which it is composed may be considered to be bounded by a frame, the parts of which have the general name of bordering pieces. Those which join the wall are the
wall-plates ; that ai the meeting of two faces, parallel to the or the junction of two planes in such a manner as to wall-plates, is the ridge-piece; and the inclined bars extend form hollows the reverse of hips. When two faces of a ing from the wall-plates to the ridge-piece are rafters, those roof join so as to form an angle similar to a valley, but in an which form the salient angles in hipped roofs being distinhorizontal instead of an inclined position, the term gutter is guished as hip-rufters. The support necessary for the exapplied instead of valley.
ternal covering is given by a series of rafters or inclined bars, A further distinction, which it may be well to mention be-extending from the wall-plates to the ridge-piece, and placed fore entering upon the details of construction, is that be
• A square of roofing contains 100 square feet.
parallel with each other at equal distances. In a hipped | roof, the purlins may, as shown in fig. 15, be notched into roof, the rafters near the ends, being parallel with the others, the principals and common rafters, but this practice is not are necessarily diminished in length, extending from the to be recommended, as it weakens the timbers. Where wall-plate to the hip-rafter instead of the ridge-piece. All principals are used, their lower ends are mortised into the such pieces, being shorter than the length between the wall- | ends of a tie-beam, which stretches across the building, and plate and the ridge-piece, are called jack rafters.
rests upon the wall-plates. This beam keeps the lower exIt is not usual to vary the scantling, or transverse dimen- | tremities of the principals from separating, and discharges sions of rafters, in any considerable degree, on account of the weight of the roof on the walls in a vertical direction, their various lengths; nearly the same scantling being used relieving them entirely from the lateral thrust of the in all buildings, and the required strength being obtained rafters. The triangular frame formed by the two principals by introducing intermediate supports between the walland a tie-beam, with any bars it may comprise for additional plates and ridge-piece where the size of the roof renders strength, is called a truss, and such frames being placed at such necessary. This additional support is supplied by regular intervals, the timber-work between any two of horizontal rectangular bars called purlins, placed under the them is called a bay of roofing. The lower extremities of rafters in such a manner as to divide their length into two the common rafters, being elevated by this arrangement or more equal parts, the ends of the purlins being fixed to above the wall-plates, are supported by pole-plates, or pieces the sides of the bordering frame. Like the rafters, the of timber parallel to the wall-plates, resting on the ends of purlins are not much varied in thickness according to the the tie-beams. The supporting frame-work altogether is strain upon them, but they are in turn supported by a series called a carcass-roof. of bars placed equidistant from each other, and parallel Fig. 7, which represents a small carcass-roof supported with the rafters, but with their upper face in the same by four trusses, and having one purlin only between the plane as the lower face of the purlins. These are called wall-plate and ridge-piece, may assist the reader in comprincipal rafters, or, for brevity, principals, to distinguish prehending the arrangement of the parts enumerated; and them from the first described, or common rafters. Where their names will be found more distinctly by referring to it is desirable to save room by reducing the thickness of a the representation of a more complicated truss at fig. 11.
In this figure the common rafters are represented on one of the rafters, relieves the walls of lateral strain. If the half of the roof only, that the trusses may be more dis- tension of the tie-beam ac be sufficient to resist the extendtinctly seen; and the end walls are omitted for the same ing force of the rafters without sensible elongation, the only reason.
effect that such a roof can have upon the walls is a vertical The proper construction of the trusses of a roof, with re
pressure on each, equal to half its weight; and it cannot ference to the size of the building and the weight of the fall without the tie-beam, which acts the part of a cord or covering, is a matter requiring much scientific knowledge. chain, being pulled asunder, or the rafters being crushed. For the want of this it is not unusual to encumber trusses If the materials were perfectly rigid, no additional parts with much more timber than is necessary or useful; and would be required; but as they are not so in practice, it the disadvantage of this is not confined to the increased becomes necessary, when the timbers are of considerable weight and cost of the roof, as superabundant timbers fre- length, to provide means for counteracting their tendency to quently occasion injurious strains, and the increased num- sinking, or sagging. By adding a bar shaped like bd (fig. ber of joints adds to the risk of derangement by the shrink- 10), the centre of the tie-beam may be suspended from the ing and warping common to all timber constructions. The crown of the roof. This piece is called a king-post, but the general principles to be acted upon may be illustrated by a
b few diagrams; but in the limited space devoted to this article no attempt can be made to describe all the modifications required by the ever-varying forms of buildings; in
hg. 10. the design of which it is too common, instead of assigning its due importance to the roof, to treat it as an unsightly feature, to be concealed as much as possible from view.
In a roof formed as shown in fig. 8, consisting simply of two inclined planes abutting on the walls, it is evident that the weight of the rafters að and bc, as well as that of the covering sustained by them, will have a tendency to thrust name is perhaps not a good one, as, though it appears like out the walls. This tendency ordinary walls have not the a post to support the ridge or crown of the roof, it is in
reality a tie, supported by it, and sustaining, instead of resting upon, the centre of the tie-beam. By cutting the king-post out of a piece of wood of larger scantling than the shank of the post itself, projections of the shape indi
cated in the cut may be formed at its ends. These are called Fig. 9.
joggles, and those at the upper end form a wedge between
the heads of the rafters, like the key-stone of an arch. It is strength to resist, and therefore it becomes necessary to add evident that a weight pressing on the projecting joggles at the beam ac (fig. 9), which, by receiving the outward thrust the base of the king-post will be by it transmitied to the
crown of the roof. These therefore form fixed points, from formed of slender rods of wrought-iron; but the others, which support may be obtained, by means of struts or ; needing stiffaess as well as cuhesion, require bars of conbraces, e and f, for the centre of each rafter. Where pur: siderable substance, and are therefore mostly formed of lins are added, they rest on those points of the principal wood or cast-iron. Sometimes the king-post is dispensed rafters that are thus supported by struts, as may be seen by with, and its office performed by two similar posts, called reference to fig. 7. It may be observed that this truss con
queen-posts, at equal distances from the centre of the truss. sists of two pieces (the tie-beam and king-post) in a state of In order to keep these in their right position, a short horitension, and four (the two rafters and the two struts) in a
zontal beam, called a collar-beam, is inserted between their state of compression; and that in every well-contrived upper extremities, and another, termed a straining sill, truss, however the number of its component parts may be between their lower ends. This arrangement is explained increased, every bar is in one or other of these states. Those by fig. 11, which also shows the position of other parts of parts which are in a state of tension, acting merely as cords a truss. One side is represented as a gutter-roof, and the to bind the truss together, may be and sometimes are' other with eaves.
aa, Wall-plates 6, Tie-beam.cc Pricipal rafters..dddd, Purlins.ee, Pole-plates. ff. Common rafters. g, King post
h, Collar-beam. ii, Queen-posts, k, Sıraining-sill. ili Struts or braces. mm, Auxiliary rafters. 7, Ridge-piece. T'he auriliary or cushion rajlers, m, m, are pieces occa
curve; and a' b'd' de', in the same figure, represents the sionally added, in large roofs, to strengthen the principals; corresponding position in which they should be vlaced in and they, with the collar-beam, &c., form a complete truss an equally loaded roof. If the rafters bc and c' d' are to within them. The trusses of truncated roofs are formed in this manner, the collar-beam forming, as it were, the keystone of the arch, and being surmounted by a camber-beam, the upper edge of which is formed into two slightly inclined planes, to give the necessary slope to the lead covering. In such a roof, pieces of wood resembling ridge-pieces are inserted at the angles formed by the meeting of the rafters
Fig. 14. with the horizontal bars that support the flat.
The following representation of a very simple truss, from Nicholson's 'Carpenter and Joiner's Companion,' illustrates the use of slender king-posts and queen-posts of wroughtiron, and shows how the stress of every part of the roof may be brought to bear on the ridge. The lower ends of the struts rest in stirrups attached to the vertical rods, and the weight bear a greater weight than a' b' and d' e', they will, if pro
portionately loaded when suspended in a curve, fall in such
a way as to increase the angles abc and cde, and diminisha Fig. 12
bcd, thereby indicating their proper position in the roof. When the roof is to be loaded unequally, and more on one side of the ridge than the other, as it would be if i'd were to be covered with lead, and the other planes with slates, a corresponding weight added to the centre of gravity of bc will cause the bars to arrange themselves as abcde, fig. 14, the angles of which, being transferred to the roof, give the
position of equilibrium a' b'd' d'e'. This practical method bearing on the strut a is imparted, through b and c, to the of finding the proper angles of a curb-roof may be applied king-post. The tie-beam is suspended by bolts from each under all circumstances, the dimensions of the experimental of the vertical rods, and the ends of the rafters are secured bars being proportionate to those of the rafters, and their to the tie-beam by iron straps passing round them, and centres of gravity being loaded according to the pressure to bolted to the beam at d, d. Trusses on the same principle be sustained by each plane of the roof. The great advanmay be made of timber only.
tage of curb-roofs consists in the space they afford for chamIn curb roofs the upper rows of rafters are called curb-bers in the roof, such chambers being lighted by dormer rafters, and the horizontal bars that receive the upper ends windows in the lower inclined faces. When the trusses of of the lower rafters, and the feet of the curb-rafters, are the roof form partitions between the bed-rooms, their posts known as curb-plates. The proper position of equilibrium and braces are so arranged as to leave one or more door. for the rafters of a curb-roof may be ascertained by very ways for communication between them. simple means, within the reach of persons not possessed of In roofs of very large span it is often desirable, in order sufficient mathematical knowledge for determining it by i to avoid running up to a great height, to form two or more calculation. If the rafters are to be equally loaded, as in a ridges. When intermediate support can be obtained from roof entirely covered with one material, this position will be partition walls, such constructions may be regarded as comexactly the reverse of that which they would take by gravity, binations of two or more distinct roofs placed side by side. were they suspended in a chain or festoon, the joints being Fig. 15 is an example of a roof of large span without any Hexible. If they are framed together in this position of intermediate support, and having a large available space equilibrium, they will balance each other like the stones of between the tie and collar beams. It represents the form an arch; and the tie-beams, posts, and braces will have no of the trusses, which were placed fifteen feet apart, of a roof other office to perform than that of resisting such irregular of eighty feet span, erected over Drury-Lane Tlieatre in strains as might tend to alter their arrangement. The ! 1793. rafters thus suspended would fall into the position abcde, It is sometimes necessary, in order to obtain additional Ag. 13, a line drawn through the angles being a catenarian height insiile a building, to raise the tie-beam above the P. C., No. 1245