Since the « Oil Crisis » of 1973 increasing attention has been paid to the supply and to the availability of the supply of energy. In particular, there has, over the past few years, been a reversal of the attitude that there is an adequate supply of oil for use by an expanding world economy and a number of increasingly pessemistic views have reveived wide publicity. We shall not, here, continue our arguments that these studies are overly pessemistic. We think it necessary to point out, however, that the modification of the world energy system to accommodate a new major energy source will be a lengthy, complicated and expensive affair; whether that new source is coal, nuclear (fission or fusion), solar, saltwater/freshwater ion transfer or rubber bands.