The destruction caused by an explosion is determined by the work which the steam or the liquid can do in expanding from its initial volume to the volume which it should occupy at atmospheric pressure. And this work depends as much on the change in volume as on the amount of pressure. Steam, like gas, has great compressability, while liquids have very little; therefore compressed steam even at a comparatively low pressure (e.g. 15 atm) can do much more work in expanding than a liquid can, even though the latter is at a very much higher pressure (e.g. 600 atm), for the increase in the volume of the gas while its pressure falls to 1 atm is incomparably greater than the liquid's increase during its fall of pressure. In fact, if steam is under a pressure of 15 atm, then its volume will increase 15-fold in reaching atmospheric pressure. But water which starts at a pressure of 600 atm increases its volume by only 0⋅03 of its initial volume in reaching atmospheric pressure.