Nineteenth century engineers knew all about the effects of thermal expansion of iron and steel. Suspension bridges rose and fell with the seasons, and railway lines were built with gaps between the rails.

   The physics instructor could demonstrate thermal expansion in the classroom with a pyrometer, but if the weather was freezing he could fill the cast iron bomb to the top with water, screw in the plug securely, and then place the bomb outside in a secure place. After a time, the bomb would fracture, more or less catastrophically. This unused example is at Union College in Schenectady, New York.