

Until'. 



in 



uo, may illustrate thin, uitl < xemplify al-.. .-.'H..- { the 

 amlinlioti- i tin- ti..p Ly which tin 1 



ung an uny fa<*, and 

 Ux tr|. a* imi.y aiUM, u there we trusMw in the r.->f. 



.li the iiiiinU i n of roofs u 



wry |rr**i, M way be wen by fair'' -ik n earpeiitiy, 



allusion CM here be made to only oue <T two other*. All admirably 

 ninple plan for making a vrry Bat r. W i described in tin- "7th volume 

 ol the ' TtinsagHoM ' of the .- \rt*. in n communication from 



tl.. inventor, Mr. Smart. The beaum or rafter* arc cut, with a circular 

 aw. a* abown at a, fg. SS, while / rvpiw nt their form when in u.-e. 



C'ol.inrl Kmy, p-ner.illy B|waliing, li.-i.l :i sj.:m of .ilmut 



sketch of ..no ,.i tln-m ! appended (/< .li-.<i-i-ii)tion c,f the 



tit- 



vnlge being inMtted between the endg of the parts that arc elevated 

 into a alopioK poaition. These may be rained to an angle of 10 or 

 12*. and will boar a erv.it weight, a* they cannot be depressed without 

 I hrwrfinx off the end* of the beam, or breaking the lower ]>art of it by 

 tendon. Th i called, by the inventor, the bow and string rafi 

 m* need by him to support n roof at the Ordnnnoe Wharf, \\'<-st- 

 minMcr Bridpe. Strung laths were nailed upon the rafters, and on these 

 a platform of bricks was bud in cement, the whole beinjf cover. 

 tile* alio bedded and pointed with cement, and twice coated witli hot 

 lin*rd-oil. The cost of this roof is stated to be not more than half 

 that of lead. 



About thirty yearn nce Colonel Kmy, of tlie French (le'nie 

 Militju're, ap|>lied, on a large wale, the system of bending thin planks 

 into an-hed ribs to support the rafters of roofs of considerable span, 

 meted over riding schools and building slips, Ac. ; and the system has 

 alco been applied in the construction of timber bridges for railways, 

 with clear openings even of 133 feet. For the latter purpose the 

 laminated timber arches have failed, on account of the entrance of 

 moisture between the separate lamina;, and the consequent rotting of 

 the UMIILS ; but in roofs, or in other positions where the arches are 

 not expoeed to occasional efforts of a nature to cause the lamina) to 

 o|>en. the beams do not rot, and there seem to be decided economical 

 advantage* in the application of Colonel Emy's system. It has been 

 introduced in the Great Northern Railway Station in London, and in the 

 ftation of the Baden Hallway, at Freiburg, with great success ; in both 

 > the spans are not less than 100 feet ; the riding schools built by 



Fig. 24. Riding School or Maroc. 



mode of putting the principals together is to be found in Emy's very 

 valuable 'Traite de la Charpenterie.' 



Colonel Ardant, also of the French Gdnie, has however published a 



FI. JS. Ardant'i Hoof. 



. ,T'T l1 '" ft n.ie ,...,,, v; i,, 



which be show, that three bent timLer principals are not ' a.lv'an- 



rong. u built beam, of a polv, ;i ] f,,,,,,. ,,f ,,,,,,,,e 



..lyframe.! n,,.l r . The great objec-ti'n ,, 



thebent i,,,,l,, r nl* i ,, v ,,,],., ^ ant ^ 



ie straight lin... , ir . , 

 tb> rbmicity of the lannmp gave rise to a c<-i. 



1 i . 2fi. Roof of HIP Hiding School, Met/. 



tt-ii.li-d to thniHt out Hi.' side walls; and in f.u I tliis >lan T.T was 



:''tually found to exist at the Great Northern Bail way Station, London, 



to so great an extent as nearly to lead to the overthrow of the wlml.; 



. l.eil. It would, however, bo easy at anytime to counteract the 



| thrust o-f a principal of thia description, and the Lent timU'r ribs are 



I no doubt viry convenient and economieal in many piwtions. Local 



I considerations, therefore, ought alone to determine the .election of 



