Page:The American Boy's Handy Book edition 1.djvu/117

water-tight. Fix the glass in one end of the box, and leave the other end open to admit the eyes of the observer, as shown in the illustration (Fig. 60).

Fig. 60.Wooden Water-Telescopes.

is a funnel-shaped tin horn, about three or four feet long, eight to ten inches in diameter at the bottom, and broad enough at the top to admit both eyes of the observer (Fig. 61). Sinkers should be soldered on near the bottom, as shown in the illustration (Fig. 61). This in a measure counteracts the buoyancy of the air contained in the water-tight funnel, and helps to submerge the big end.

Fig. 61.A Tin Water-Telescope.

The inside of the funnel should be painted black, to prevent the light from being reflected upon the bright surface of the tin.

If any difficulty is found in procuring a circular piece of glass, the bottom may be made square and square glass used, and fitted into a leaden frame made for the purpose.