6 THE president's ANNUAL ADDRESS. 



untwisted strand of sewing silk, or much better of a few fragments 

 of the raw material, which may be had from a silk-worm fancier, and 

 which can be mounted in the same way. These, with some raw 

 flax fibres from a piece of genuine linen, a little sheep's wool, and 

 some rabbit's and seal's fur, will form a useful set of standard slides. 



Cotton comes from the pod of the cotton plant. Each fibre is 

 like a twisted strap, or waved ribbon, which enables it to obtain 

 a hold or grip on its neighbours. A similar hold is obtained in 

 woollen fibres by the projecting scales, which are so familiar to 

 us in the human hair, and the interlocking of these scales 

 produces in cloth the effect known as felting. 



The character of a fabric consisting of a mixture of cotton 

 and wool is thus at once revealed, when the texture has been 

 broken up and spread on a slide. (In describing these structures 

 the term " fibre " is applied to the simplest elements to which 

 any tissue can be reduced.) Linen fibres consist of the fibro. 

 vascular bundles of the Limiin stem, which have been separated 

 by beating, by which operation they are not only divided, but 

 bruised and softened. When examined under the microscope 

 just after removal from the plant, the fibres are smooth 

 cylinders of almost uniform diameter ; but after the process of 

 *' scutching," as the preparatory beating is called, each fibre 

 shows several transverse fractures. Cotton and linen fabrics are 

 thus distinguishable by the twisted-tape-like appearance of the 

 former, and the resemblance of the latter to bruised straw. 



It is a more important matter to be able clearly to determine 

 what is and what is not silk ; the chief admixture in fabrics of 

 this kind is with cotton, whose characters have just been noted. 

 The fibre of silk is smooth, apparently double, and of uniform 

 diameter, the two halves of each thread being produced from 

 different spinnerets of the silk-worm. Silk is a viscid secretion, 

 which solidifies as it exudes. 



Fur is worthy of examination. Very much of that which is sold 

 for trimming ladies' dress is dyed to resemble the fur of the 

 animal whose name it bears, but has really come from the back 

 of the rabbit. This may be proved by mounting a few of the hairs 

 in glycerine jelly. The hair of the rabbit appears very much like 

 a ladder. Seal fur is not of uniform diameter, and somewhat 



