ON THE STRENGTH OF MATERIALS. 117 



The strength of a structure depends, in a very great degree, on the manner 

 in which the several parts are joined together, and by a skillful combination, 

 or interlocldng, verj- weak and fragile materials may be made to resist the 

 action of powerful forces. Examples of this occur in the manufacture of 

 ropes, strings, thread, etc. : in the weaving of baskets, and especially in the 

 structure of cloth ; in this last instance, a series of parallel threads called the 

 jijQ gg woof, is made to interlock with 



another series of threads called 



— ^D-T n^'T^M ^"^'^^'"T *^® warp, running transversely 



— '[ — nTprT ZJ~piI~rJ~ rL | _LL| | _iL| [-. across, and passing alternately 



"iNf 1^ ^TT In^ In^ i^:l^iHr ^^^'' ^^'^ under the first series. 



7P1 1^. 1^ i^ 1^. I^rponlf Fig. 98 represents the appear- 



j]^£|~irpr]^J~bt]~^^ ance of a piece of plain cloth 



it pH^ n prx JTT- Inr In^' 'n~hT^ seen through the microscope; 



dtjUL p Op brgprT. iTpJinl ~ the alternate mtersections of 



■ 11 II n II II iml II iririml ii ilii 



the threads are seen in the 



•=s%*^Sn«.*:^«^«.«,^=^ «/i=^..-^^-.-« « <^ lower figure, the dots repre- 



Bcntmg the ends of the warp 

 threads, and the cross line the wooC 



263. When a single beam can not be found deep enough 

 to have the strength required in any particular case, several 

 beams may be joined together, in a variety of vrays, so that 

 very great strength is obtained without a very great increase 

 of bulk. Such methods of joining timber are known as 

 scarfing and interlocking, tonguing, dovetailing, mortis- 

 ing, etc. 



'OJ 



Fig. 99. 



264. Scarfing and interlocking is the methoi 

 ing and inter- of inscrtlou iu whicli the ends of pieces over- 



locking 



lay each other, and are indented together, so 

 as to resist the longitudinal strain by extension, as in tie 

 bearers and the ends of hoops. (See Fig. 99.) 



265. Tong-uino; is that method of inbcrtion in which the 



