Page:Popular Science Monthly Volume 22.djvu/512

496 to what metal was used. With Wood's alloy, which is very fusible, the projections that fell on the edge of the crater flowed away, and left no trace of their passage. With the second alloy the projections



all continued visible, and gave a rent aspect to the crater. Moreover, since the warm air was not hot enough to melt the metal, the projections might eventually overhang the bottom, as appears in Fig. 1.



"The second experiment was marked by a very interesting incident. Two concentric circular areas were noticed, the one nearer to the center being the higher. This was due to an interruption to the