The origins and growth of any industry can be traced to a number of major impelling forces. In the case of any given industry, therefore, it may be possible to throw some light on probable future developments by studying the history of its evolution from its origins right up to the present time. By this means, some assessment may be achieved as to the future requirements of the industry and as to what policy should be supported in order to meet these requirements in the best way. In particular, it may be possible to discern specific trends and to foresee the speed at which these should come to maturity, what obstacles may be encountered, and how best to prepare for such difficulties in advance.