Page:Popular Science Monthly Volume 5.djvu/417

Rh lines are portions which have become liquid. We have seen that freezing is a process in which water expands in volume. This implies change in its molecular structure, or that the molecules assume new positions. Perhaps the wonderful movement of particles around the poles of a magnet, illustrated by Fig. 2, may suggest the nature of the interior movements which occur in the crystallization of water. Certain it is that the molecules recede from each other and occupy more space than when they lay compacted in the liquid condition.



Water expands, in freezing, with a force that is practically irresistible, its increase in volume being about ten per cent. Flasks of copper and iron are broken by it. Rocks are split asunder and disintegrated, and from this cause the freezing of water plays an important part in geological changes. A bomb-shell filled with water and closed by an iron stopper was exposed to frost; in a little time the stopper



was driven out to a distance of several hundred feet, and a mass of ice protruded. In another case the shell burst, and a sheet of ice expanded around the crevice. These tremendous mechanical effects are shown in Fig. 3. In these and similar cases the water may not have