30 ENGINEERING ON THE FARM 



composing it are untwisted, but the yarns in the strands 

 are again twisted up. It is this opposite twist that keeps 

 the rope from untwisting. When a weight is hung at the 

 end of a rope, the tendency is for the rope to untwist and 

 become longer. The weight will revolve until the strain 

 of the rope trying to untwist is just balanced by the strain 

 of the strands being twisted up. All makers of rope twist 

 them in the same direction ; otherwise it would not always 

 be possible to splice ropes obtained from the different 

 factories. 



Sources of fiber. Many different vegetable fibers are 

 used for rope making. The most common ones are Manila, 

 or Manila hemp, common hemp, sisal hemp, and cotton. 

 Flax, jute, coir fiber, and other materials are also used. 



Manila fiber is obtained from the abaca plant, which grows 

 only in the Philippine Islands. It obtains its name from 

 the city of Manila, from which most of it is exported. The 

 trunk of this plant resembles the banana tree and is closely 

 wrapped by long leaves which yield fibers from 6 to 12, and 

 even 18, feet in length. 



Common hemp is an annual herb of the nettle family, 

 from 4 to 8 feet high. It has green flowers and a tough, 

 fibrous inner bark. The tough, strong fibers obtained from 

 the inner bark are used in making coarse cloth and rope. 



Sisal hemp comes principally from Yucatan and Mexico. 

 Its fiber is especially valuable for ship cables, as it seems 

 to resist the action of sea water better than most other 

 materials. 



Cotton is planted annually in the United States and is 

 the staple agricultural product of our southern states. The 

 commercial cotton is the soft, woolly, fibrous material which 

 is attached to the seeds of the cotton plant. The fiber is 

 white or yellow, and from two-thirds of an inch or less to 

 2 inches long. The fibers are contained in a three- to five- 

 celled capsule or boll which bursts open when ripe and 

 allows the fibers to escape. After the seeds are removed, 



