As when by putting a lighted match to fuel,and water into a boiler over it,he generates the expansive force of steam,a power which has been made so largely available for the attainment of human purposes.

• 例如，人用点着的火柴引燃燃料并把水放进燃料上面的锅炉中，便可产生蒸汽的膨胀力，人类已广泛利用这种力来达到各种目的。