What to do and how to do it; the American boys handy book (1920)
Beard, Daniel Carter, 1850-1941 · New York, C. Scribner's sons · leaf 113
Fig. 60.—Wooden Water-Telescopes. A Tin Water-Telescope, IS a funnel-shaped tin horn, about three or four feet long, eightto ten inches in diameter at the bottom, and broad enough atthe top to admit both eyes of the observer (Fig. 61). Sinkersshould be soldered on near the bottom, as shown in the… … Fig. 61.—A Tin Water-Telescope. the air contained in the water-tight funnel, and helps to sub-merge the big end. The inside of the funnel should be painted black, to preventthe light from being reflected upon the bright surface of the tin. If any difficulty is found in procuring a circular piece of…
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