The physicist, in his endeavour to explain natural phenomena, has, in the course of his investigations and observations, discovered certain laws which appear to be constant and applicable to the phenomena in question. On the basis of those laws he has evolved theories which provide him with an intelligible appreciation of the mechanism involved. The law embraces and synthetizes a large number of observations, but it also serves as a point of departure for new observations. Whilst the law may be constant, the theories may undergo modification, as new facts come to light, as has occurred, for example, in the case of the atomic theory. Amongst physicists there is, however, a readiness to consider new discoveries, to put them to the test, and, if they are found to be in harmony with determined laws, to incorporate them in the theoretical scheme.