Mr. Peter Mason (Past President): The subject of this paper is, of course, fascinating-experiences that we have all had, but that we do not normally attempt to analyse or put into graph form. In Table 3 the author shows relative accelerations for different sets of circumstances. Particularly interesting to me were those for earthquakes-something like 45 m/s to the power 2-and those for a fairground machine, which were also up to 45 m/s to the power 2. Yet the human reaction to these experiences was completely different-the reaction to one being horror and, to the other, pleasure. I wonder what is the mechanistic explanation. Is there a factor in the earthquake motion additional to that of the machine? Is there, indeed, some factor of which we are unaware (or possibly do not recognise) that is additional to the normal accelerations and movements that can be measured in three dimensions? Or do these reactions differ so widely because of the psychological pressures of being in a red danger situation as compared with being in a simulated one-even though (or perhaps because of the fact that) the simulated situation often does contain an element of real danger?