Among the experiments undertaken with the aim of establishing the properties of the propagation of light by direct measurements, quoted earlier, we mentioned the Michelson-Morley experiment as having a special bearing on Einstein's conceptual edifice. It is the one which has formed the foundation of that (earlier) part of Einstein's theory which he himself called the Special Theory of Relativity. Let us see what becomes of this foundation - and with it the conceptual edifice erected upon it - when we examine it against the background of what we have found to be the true nature of the so-called velocity of light.