The Boy's Playbook of Science / Including the Various Manipulations and Arrangements of Chemical and Philosophical Apparatus Required for the Successful Performance of Scientific Experiments in Illustration of the Elementary Branches of Chemistry and Natural Philosophy

by John Henry Pepper

Fig. 277.

The smoke shows the rays of light falling on a convex mirror, and rendered still more divergent.

The smoke developes the cone of rays reflected from a concave mirror in the most beautiful manner, and by producing plenty of smoke, and turning the mirror about—the position of the focus (focus, a fire-place), is indicated by a brilliant spot of light, and the reason the images of objects reflected by the concave mirror are reversed, may be better understood by observing how the rays cross each other at that point. (Fig. 278.)

Fig. 278.

The smoke shows rays of light falling on the concave mirror. In this experiment attention should be directed to the bright point, e, the focus where the convergent rays meet.

One of the most perfect applications of the reflection of light is shown in the "Gregorian reflecting telescope," or in that magnificent instrument constructed by Lord Rosse, at Parsonstown, in Ireland. (Fig. 279.)

Fig. 279.

Lord Rosse's gigantic telescope.