of the basin, and you were thus enabled to see the articles at the bottom.
I have shewn you this experiment first, so that you might understand how glass attracts light, and might then see how other substances, like rock-salt and calcareous spar, mica, and other stones, would affect the light; and, if Dr. Tyndall will be good enough to let us use his light again, we will first of all shew you how it may be bent by a piece of glass (fig. 19). 
Fig. 19.[The electric lamp was again lit, and the beam of parallel rays of light which it emitted was bent about and decomposed by means of the prism.] Now, here you see, if I send the light through this piece of plain glass, A, it goes straight through, without being bent, unless the glass be held obliquely, and then the phenomenon becomes more complicated;
