160 MAC HINT. I 'RAWING AND DEftHA 



advantage over ordinary bronze, that it may bo n nu lt< .1 

 without deteriorating in quality. This alloy also l::i- tin 

 advantage that it may be made to possess groat strength 

 accompanied with hardness, or less strength with a hi.u'h 

 degree of ton gh ness. 



Wood. In the early days of machines wood was largely 

 used in their construction, bat it is now nsed to a very limit' <i 

 extent in that direction. Jieech and hornbeam are nsed for 

 the cogs of mortise wheels. Yellow pine is much used by 

 pattern-makers, /tor, a heavy, hard, yellow- coloured wood, 

 is nsed for the sheaves of pulley blocks, and sometimes for 

 bearings in machines. Lignv is a very hard dark 



coloured wood, and remarkable for its high specific gravity, 

 being 1J times the weight of the same volume of w. 

 This wood is much used for bearings of machines which arc 

 under water. 



TABLES OF STRENGTH OF MATK1M A I .>. 



fLTIMATE TENSILE STRENGTH 



Approximate average values in tons per squun 



ron s Xinr. i-t.-t . . HI 



lit-iron short .... 7 



. good quality . . '!'.' Iir.n/.- (("inn n 



Bare, superior quality i'7 < ']>] r, <J'J ; tin, 8 . , !" 



:ng . lil r,,]i|M.-r. '.n : tin, 10 . . I . 



1 (juality PhosplKtr-broTize . 



A) in . . -Jl M .: - 



r<8 . 19 Brass, y.-llcw 



l'l;it< s, xiiprrior qualit} Muntx-in 



A1..HL' tlio grain . " . lf| 



Acrow . . L'l 1). hn-n.etal, cast . 



r..ll-.l . . 30 



QMtiagl . ''" i Wood (along the fibres) 



n^ .... 30 Ash .... 



.Mild stoc-1 bar. . ! : oh 



M. 1.1 Hteel plates . Kin, 



Copper Fir aii'l piin- 



Cast 10 M 



d . . . Lignuni-vii. 



I Oak . 

 . 1 5 



