The Story of the Cotton Plant - Frederick Wilkinson

Then again in the same boll all fibres do not ripen together just as all apples on the same tree do not ripen together.

Immature or unripe cotton cannot be dyed, and when small white specks are seen in any dyed fabric they are often due to the fact that unripe cotton has been used in the manufacture of the cloth.

Measurement of the Cotton Fibre.—This is not at all a difficult matter, and the ordinary student may, by means of very simple and inexpensive apparatus, obtain fairly satisfactory results in the measurement of fibres.

There is a choice of one of three methods, viz.:—

1. By having the mechanical stage so arranged that the slightest displacement either to the left or right can be measured, and having the eye-piece so marked (generally a hair stretched across it) that when an object is to be measured, one side of it is made to coincide with this central line and the stage rack is worked left or right until the opposite side of the object is brought coincident with the central line again; the amount of displacement can then be readily obtained on referring to the graduated stage.

2. By having a stage micrometer and camera lucida.

3. By having two micrometers, a stage micrometer and eye-piece micrometer.

This latter method is certainly the least expensive, and for all practical purposes can be safely recommended.

A stage micrometer consists of a slip of glass 3" × 1" on which are marked divisions of an inch, usually ¹⁄100ths and ¹⁄1000ths. As a rule these markings are protected by means of a small cover-glass.

Eye-piece micrometers vary much in form, size and value, but the one which is here described is of the simplest type. It consists of two circular pieces of glass carefully cemented together. On one of the inner surfaces are marked usually the ¹⁄100ths divisions of an inch. In some ¹⁄200ths are marked. If the top lense of the eye-piece be unscrewed, a diaphragm will be found on which the eye-piece micrometer will easily rest. Screw on the top lense again and, generally, the eye-piece will be ready for use. If the micrometer is not properly in focus after a few trials, it may easily be made right. In order, then, to measure the diameter of a single fibre of Sea Islands cotton, fit in the quarter inch objective and place the stage micrometer in position on the stage. First, focus the fine lines which are plainly to be seen, and remember the lines which are farthest apart are ¹⁄100th of an inch; the others ¹⁄1000th of an inch.