The very nature of the ªfirst halfº has meant that development and utilisation of energy resources has been a mainspring from which so much of the progress made has been derived. In reflecting upon the progressive use of energy it is striking to note the great increases in efficiency that have characteristically been applied. An early example is that of the efficiency of the reciprocating steam engine, and Table 1 shows the hard won progress from the days of James Watt, over the following period of what might be called initial development.