ON THE UNION OF FLEXIBLE FIBRES. 183 



male and female flowers of liemp are on different plants ; the male plants are 

 soonest ripe, and require to be first pulled. They are prepared for dressing by 

 being exposed to the air, and the fibrous part is separated from the dry pulp 

 by beating and hackling. In spinning the yarn, the hemp is fastened round 

 the waist; the wheel is turned by an assistant, and the spinner, walking back- 

 wai-ds, draws out the fibres with his hands. When one length of the walk 

 lias been spun, it is immediately reeled, to prevent its untwisting. The ma- 

 chines employed in continuing the process of ropemaking are of simple con- 

 struction, but both skill and attention are required in applying them so as to 

 produce an equable texture in every part of the rope. The tendency of two 

 strands to twist, in consequence of the tension arising from the original twist 

 of the yarns, is not sufficient to procure an equilibrium, because of the friction 

 and rigidity to be overcome; hence it is necessary to employ force in order to 

 assist this tendency, and the strands or ropes afterwards retain spontaneously 

 the form which has thus been given them: the largest ropes even require ex- 

 ternal force in order to make them twist at alL 



The constituent ropes of a common cable, when separate, are stronger than 

 the cable, in the proportion of about 4 to 3 ; and a rope worked up from yarns 

 180 yards in length to 135 yards, has been found to be stronger than when 

 reduced to lao yards, in the ratio of 6 to 5. The difference is owing partly 

 to the obliquity of the fibres, and partly to the unecjual tension produced by 

 twisting. Mr. Huddart's ropes of 100 yarns lose but about one eighth of the 

 whole strength of the yarns ; and his experiments appear to show that similar 

 ropes made in the common manner retain only one half of their original strength. 

 The tarring of ropes, although sometimes necessary for their preservation from 

 decay, is found to lessen their strength, probably because it produces partial ad- 

 hesions between some of the fibres, which cause them to be disproportionully 

 strained. A rope is also said to be weaker when wet than when dry, perhaps 

 because the water enables the fibres to slide more readily on each other, or be- 

 cause the presence of water is in general favourable to separation of any kind. 

 A good hempen rope will support, without danger, one fifth as many tons as 

 the square of its circumference contains inches. 



Flax is weaker than hemp, but not less extensively useful. Its growth 

 considerably exhausts the strength of the soil which produces it; its cultiva- 



