Light; a course of experimental optics, chiefly with the lantern . Fig. ? Effects of Sonorous Vibrations. inserted, some other colour oi that will appear. Orwe may vary the experiment by putting in the arrange-ment for heating glass. Starting with a dark field, oninserting the hot iron bar we get the phenomena varied by xii.] , MACHS ANALYSIS. 281 the effects of /^^aZ-vibrations ; and when we have got goodcolour, we vary these again by interposing .f^««( experiment can be very fairly performed with theArgand burner, and a screen distance of about 4^ feet,giving a disc of
Light; a course of experimental optics, chiefly with the lantern . Fig. ? Effects of Sonorous Vibrations. inserted, some other colour oi that will appear. Orwe may vary the experiment by putting in the arrange-ment for heating glass. Starting with a dark field, oninserting the hot iron bar we get the phenomena varied by xii.] , MACHS ANALYSIS. 281 the effects of /^^aZ-vibrations ; and when we have got goodcolour, we vary these again by interposing .f^««( experiment can be very fairly performed with theArgand burner, and a screen distance of about 4^ feet,giving a disc of 15 inches. This beautiful phenomenon is due to the stress causedin the glass near the nodal points, by the vibrations intowhich its molecules are thrown. Here, however, a difiScultymay occur to some solitary student which actually didoccur to myself, and which led me for some time to ques-tion this explanation. Dr. Tyndall himself states that,upon sounding the glass, the screen effects are rendered complementary ; and in my own experiments I alsofound this
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