So much has been written recently about the marvelous developments in mathematical physics, that we have almost forgotten that the amazing progress of science in the twentieth century was made possible as much by the skill and machinery of the instrument maker as by the genius of the theoretical physicist. The two greatest achievements of modern physics, the relativity theory and the quantum theory, are magnificient examples of the power of experimental instruments to disclose new possibilities and new realms of (...) theoretical study. (shrink)