"The whole idea of modern electrical machine theory... is based on this idea of the two independent axes, co-existing, co-related but nevertheless identifiably separate. We deal with complicated matters when we deal with rates of change of current, matters that require not only the Special Theory of Relativity, but the General Theory (the world of relative accelerations)... Might there not exist a similar complexity also in the , if rates of change of acceleration are involved? ...Work on rates of change of acceleration (American scientists have called it 'surge') is very sparse."