Abstract
Previous speakers have mentioned that the subject of the second coefficient of viscosity was first clearly and fully dealt with by Tisza in 1942. He put forward the point of view, from theoretical considerations, that the excess absorption of highfrequency sound energy in different media could be accounted for by considering the factor of the second viscosity. His theoretical deductions, however, were not in a form which could be checked experimentally. In 1947 Gurevich again pointed out this fact and showed that excess adsorption of sound in water could be satisfactorily explained but again without experimental verification. Any direct method for the experimental determination of this coefficient is still not known.