448 



R O O F. 



Roof. 



PLATE 



CCCCLXXXI. 

 *'' 15 - 



R. 16. 



"Fig. 17. 



as the space gained in the roof would amply repay the 

 cost of the lead. 



We shall now conclude this article with a brief de- 

 scription of three very ingenious roofs by foreign car- 

 penters, all of which have been described by Uonde. 

 let in his L'art de Balir, and also by Mr. Tredgold. 



1. Roof of the Basilica of St. Paul at Rome. 

 The space which this roof crosses is 78.4 feet, and it 

 is executed in fir. The trusses represented in Pkte 

 CCCCLXXXI. Fig. 15, are double, each consisting of 

 two similar frames, placed 149 inches apart. The 

 principal rafters, p, p, abut against a short king post, 

 k. A piece of timber, *, is placed between the trusses, 

 and is sustained by a strong key of wood passing 

 through it and the short king posts. This piece, *, 

 sustains the tie-beam, J, by a strong key at a. The 

 tie-beams are in two lengths, and scarfed together by 

 three iron straps. The following are the scantlings of 

 the timber : 



Inches. Inches. 



The beams/, . . 22.5 by 14.9 



Principal rafters p, . 21.75 by 14-9 



Auxiliary rafters b, . 13.8 by 13.3 



Straining beam C, . 149 by 12.8 



Parlins d, 8.5 square, and 5 feet 7 inches apart. 



Common rafters, 5.3 by 4.25, and 8.5. 



In this roof the common rafters are covered with 



strong tiles about 12'inches by 7, laid like pavement 



with mortar at the joints. Above this pavement a 



kind of plain tiles with ledges are laid, and the joints 



covered with crooked tiles. This roof is admired for 



its strength and simplicity of construction, and for the 



method of sustaining the middle of the tie-beam. 



2. Roof of the Theatre d' Argentina of Rome, Fig. 16. 



The opening which this roof covers, is 80^ feet, 

 and its inclination is 24. The tie-beam is composed 

 of three pieces, and the principal rafters of two pieces, 

 these pieces being all scarfed and strapped together. 

 The common rafters, whose distance is from 10 to 11 

 inches, supported by 12. purlins on each side, carry a 

 heavy covering of tiles. The tie-beams are very judi- 

 ciously supported by stirrups of iron, as shown in the 

 figures. This roof is of fir, and supports the machinery 

 of the theatre, besides the covering and ceilings. 



3. Roof of the Riding-house, built at Moscow, by 

 Paul I. in 1790, Fig. 17- 



This roof is the widest that has ever been construct- 

 ed. The span was 2.35 feet, and its inclination 19*. 

 The principal support of this enormous roof is a 

 curved rib of timber, consisting of three ribs indented 

 together, and strapped and bolted with iron. The tie- 

 beam consisted of seven pieces, and the principal raf- 

 ters and the tie-beams were sustained by vertical pieces 

 notched to the main rib, the whole truss being stiffened 

 with diagonal braces. This roof settled so much that 

 it was proposed to add another curved rib in the posi- 

 tion indicated by the dotted lines. The riding-house 

 was 1920 feet long and 310 wide. 



We shall now conclude this article with a list of se- 

 veral important and scientific roofs that have been ex- 

 ecuted in different parts of the world, with references 

 to the works in which they are represented and ex- 

 plained. The examination of these roofs will be an in- 

 teresting study for the young engineer, as well as for 

 the carpenter*. 



List of several roofs that have been executed in different 

 parts of Europe. 



1. Roof of the Pantheon in Oxford street, burned 

 down in 1792. Designed by Mr. James Wyatt. Art. 

 CARPENTRY in this work, Vol. V. p. 537, Plate 

 CXXVIII. Fig. 1. 



2. Roof of St. Paul's church, Covent Garden. De- 

 signed by Mr. Hardwick in 1794. Art. CARPENTRY, 

 p. 537, Plate CXXVIII. Fig. 2. 



3. Roof of the royal Hospital of Greenwich. De- 

 signed by Mr. James Stewart. Art. CARPENTRY, 

 p. 538, Plate CXXVII. Fig. 3. 



4. Roof of Southampton Church. Designed by Mr. 

 Reveley in 1797- Art. CARPENTRY, p. 538, Plate 

 CXXIX. Fig. 4. 



5. 6. 7. These roofs are designed by Mr. Peter Ni- 

 cholson^ and described under CARPENTRY, page 538, 

 and Plate CXXIX. Fig. 1, 2, 3. 



8. Roof of the old Halle au file at Paris. Design- 

 ed by Moulinier. Article CARPENTRY, page 53Q, 

 Plate CXXIX. Fig. 5. 



9. Roof designed by Mr. Peter Nicholson, for a 

 dome. Article CARPENTRY, page 53. Plate CXXIX. 

 Fig. 6. 



10. Roof of the dome of St. Paul's Cathedral, de- 

 signed by Sir Chri&topher Wren. Article CARPEN- 

 TRY, page 539, 540. Plate CXXIX. Fig. 7, 8, 9. 



11. Roof of the Theatre of the University of Ox- 

 ford, designed by Sir Christopher Wren. Dr. Robi- 

 son's Works, art. ROOF. 



12. Roof of the Caledonian or Equestrian Theatre 

 in Edinburgh, in 1809. Idem, ibid. 



13. Roof of the Birmingham Theatre. Nicholson's 

 Carpenter's Assistant, p. 6l, Plate 72. 



14> Roof of Drury Lane Theatre. Idem, ibid, p. &X 



15. Roof of Westminster School. Smith's Speci- 

 mens of British Carpentry, Plate VIII. and Tredgold's 

 Carpentry, Plate IX. Fig. 6'4. " 



16. Roof of the Basilica of St. Paul at Rome, exe- 

 cuted about four hundred years ago. Rondelet, L'Art 

 de Balir, tome iv. p. 170. Tredgold's Carpentry, 

 p. 85, and Plate X. Fig. 66; and Plate CGCCLXXXL 

 Fig. 15, of this article. 



17. Roof of the Theatre d' Argentina at Rome. 

 Rondelet, L'Art de Batir, tome iv. p> 220.. Tredgold's 

 Carpentry, p. 86, and Plate X. Fig. 69, and Plate 

 CCCCLXXXI. Fig. 16. 



18. The largest roof ever executed, being tha8 of 

 the Riding House at Moscow, erected by Paul I. in 

 1790. Krafft's Recueil de Charpente, part ii. No. 39. 

 Rondelet's L'Art de Balir, tome iv. Plate CXsVL 

 Tredgold's Carpentry, p. 87. Plate XL Fig. 7. and Plate 

 CCCCLXXXI. Fig. 17. 



19. Roof of the Royal Military Chapel at Woolwich, 

 designed by Mr. Tredgold. Tredgold's Carpentry, 

 p. 75, 226, and Plate VIII. Fig. 57. 



20. Roof of a dock for building ships under cover, 

 95 feet span. Designed by Mr. Seppings. This roof, 

 Mr. Tredgold remarks, is a fine specimen of the 

 best method of stiffening and connecting the parts, 

 but its parts are not in equilibrio. Tredgold's Carpen- 

 try, p. 18, Plate II-L Fig. 25. 



See the articles BRIDGE, CARPENTRY, JOINE-RY, 

 and STRENGTH OF MATERIALS, and the following 

 works. 



Couplet, Mem. Acad. Par. 1726, 1731. Emerson's 

 Mechanics, Fluxions, Algebra, and Miscellanies. Dr. 

 Robison's treatises on ROOF and CARPENTRY, in his 



Roof. 



