SPIRAL CURVE. 33 



pends ; the disposition to give way, or submit to some alter- 

 ation of form when pressed upon, and an energy by means 

 of which the original form is resumed, as soon as the ex- 

 ternal force is removed." These two principles are beauti- 

 fully exemplified in the fibres of wool, obviously much 

 dependant on the numerous and minute spiral curves, so 

 manifest in the Saxon and Merino. Take, for instance, a 

 single fibre of wool of these varieties of sheep, if it be 

 stretched to its full length, and then suddenly set free at one 

 extremity, it will resume its ringlet form ; and hence upon 

 the union of pliahility with the elastic principle chiefly de- 

 pends the usefulness, and consequently value of wool. 



The play of these powers is differently adjusted in differ- 

 ent wools. In the Saxon, calculated for our finest fabrics, 

 -the action of these opposing principles is beautifully bal- 

 anced. Hence it is the fabric is so easily shorn of its 

 superfluous nap, the facility with which it yields to pressure, 

 and covers the threads of the cloth with a dense, soft pile. 

 Notwithstanding the injury the elastic powers may receive 

 by the process of manufacture, yet by the aid of a micro- 

 scope, the nap presents innumerable minute curves closely 

 hugging the texture ; and to this much of the beauty of our 

 finest cloth is owing. To these opposing powers of the 

 fibre, the felting principle is not a little indebted, as will be 

 explained hereafter. 



SPIRAL CURVE. 



The spiral curve, or ringlet form of wool, has been referred 

 to. This is one of the distinguishing qualities between wool 

 and hair, the latter being comparatively straight. It is re- 

 markable in all short-wooled sheep, but in no other varieties 

 is it so conspicuous as the Saxon and Merino. It is ob- 

 servable in the Leicester and other long-wooled varieties, 

 but in a far less degree ; and with some species of the goat, 

 under the hair of which is found a perfect wool, having the 

 true felting property, and the fibre considerably curved. 



There is an intimate connexion between the fineness of 

 the wool, and the number of the curves, or otherv/ise, in pro- 

 portion to the number of curves in a given span, is the diame- 

 ter of the fibre. It should be stated, however, that this is 

 more generally true of pure Saxon and Merino. It can be 

 easily demonstrated, if the experiment is fairly made with 

 (he micrometer, care being taken not to destroy the curves 



