173 



HOOF. 



ROOK 



174 



either Emy, Ardant, or Philibert de 1'Orrae's systems of executing large ner in which the physical properties of the wood are brought into 

 timber roofs without tie-beams. In the main, they are all founded on ! action. In Emy's beam the elasticity of the bent planks is the great 

 the same principle that of introducing a rigid beam for the purpose : element of resistance ; in Ardant and de 1'Orme's principals, the wood 

 of supporting the principal rafter ; the differences consist in the man- resist* mainly efforts of compression. 



rt 



Fig. 17. Hew Street Stition, Birmingham. 



fig. >8. Lime Street Stition, Liverpool. 



Fig. 50. Terminus of Strasbourg Kailwar, ParU. 



Fig. 30. Terminal of Kouen R.iilw.ir, 



lig. 31. KntrcpAt cle Mrai, 1'arin. 



Som" illu (.rations aro appealed t the mint rnnarkalilu w 



tiecuted of late year*. principally t-> n t <\i- ropilrrmento 



of the railway cotiiinuni'-tin.-. They are, in their Ml-ct. li','ht and 



i th'HiBh cxmtly : aii'l it in precisely on nccnnnt. ol 

 rtivtic i|iia!iti"X. nrvl . ; ', tli- warping nf complicated 



ilier, .-'ifli 



pMiernlly pivi-n t" irmi HVIT . .. 



'i view, .-uirl 



I'herf. Tlie Ijent work u|H>n tin; 

 of this flu in'o, ' Lecons 



mi'|iie Pn 'it r'inark t<> l>" 



with rexpect to thene iron n.ot'i in that the xteam and HUKI^C (rum ']< 



k -niii'ititi - havi- a deleterious influence upon them; And for this 

 they cannot be, ti.-ed where the locomotives in steam are likely 

 i-iin l"n^ under thoin. 



In the valuable practical work "I Nieln.l--..ii. Ti. ! 'old, to., the 



j method* of calculating the strength necessary in the various parts of a 



r<K)f may be found ; anil in the ' Principles of (.'arpentry,' by the liitter 



'nsions Huit.ible for different spans. 



The table h*n: .iuot.f| refers to a roof similar to lirt. 7; the i. 

 being not more than ten feet apart, and the pitch at an angle of about 

 11' with the horizon, for a covering of elates. The scantling^ an; 

 suited for yellow lir, and inn t '>u Minmwliat increased for Umber "I' 

 inferior rjualit.y. 



