An early witness of the phenomenon was Ralph Bray, a young graduate student. He joined the germanium effort at Purdue University in November 1943 and was given the tricky task of measuring the spreading resistance at the metal-semiconductor contact. Bray found a great many anomalies, such as internal high-resistivity barriers in some samples of germanium. The most curious phenomenon was the exceptionally low resistance observed when voltage pulses were applied. This effect remained a mystery because nobody realised, until 1948, that Bray had observed minority carrier injection - the effect that was identified by William Shockley at Bell Labs and made the transistor a reality.