116 A HALF-HOUR WITH 



Cotton fibre. 



Hairs and scales from leaves. 



Longitudinal sections of wood. 



The first-named on our list can be very easily 

 procured by scraping a potato, and then shaking 

 the pulp in a test-tube with water, to which a 

 small quantity of soda has been added. The 

 starch will rapidly subside, and the fibrous matter, 

 &c., can be poured off. The washing should be 

 repeated until the starch is left perfectly pure. 

 Starch for polarizing purposes requires to be 

 mounted in Canada balsam. The hairs and scales 

 of plants require no preparation for mounting. 

 The scales of Eleaynus or Hippophce rhamnoides 

 (sea buckthorn) (Fig. 6, pi. 9), are easily procured, 

 and offer no difficulty to the young manipulator, 

 merely requiring to be detached from the cuticle 

 of the leaf with the point of a knife or lancet, and 

 afterwards transferred to a drop of water, to 

 which a minute quantity of gum has been pre- 

 viously added, when dry, mount in balsam. 



The following list contains a few of the objects 

 from the animal kingdom : 



Fish scales. 



Palates of Mollusca. 



Hairs. 



Quill. 



Horn. 



Whalebone. 



Fish scales are so well known that no difficulty 

 can arise in obtaining specimens, with the excep- 

 tion of those from the eel, which do not occur on 

 the surface, but will be found imbedded in the 

 skin ; they may be obtained by picking the skin 

 with the point of a needle, previously scraping off 

 the mucus. 



