from The Century Dictionary.
- noun One of the overlapping movable tubes of a field-glass or telescope.
- noun In a microscope, the tube which carries the eyepiece and object-glass. It consists of two parts, one sliding within the other, so that its length can be varied at will.
Sorry, no etymologies found.
By its means the ordinary image of one component is thrown upon the extraordinary image of the other, and the composite may be viewed by the naked eye, or through a lens of long focus, or through an opera-glass (a telescope is not so good) fitted with a sufficiently long draw-tube to see an object at that short distance with distinctness.
Inquiries into Human Faculty and Its Development Francis Galton 1866
"Two, with the draw-tube closed," replied Thorndyke, "and the low-power eye-piece brings it up to four.
The Red Thumb Mark 1902