Congestive heart failure is a common occurrence in cases of far advanced anthracosilicosis. In a series of postmortem examinations made on anthracite miners,1heart disease was found to be twice as common in the miners as in nonminers. At the White Haven Sanatorium it was noted that the most common symptom of the anthracite miners was dyspnea of varying severity, and it was difficult at the time of admission to determine whether this dyspnea was due to cardiac insufficiency or to anthracosilicosis. Attempts have been made to determine whether dyspnea in such cases is cardiac or pulmonary in origin by studying the vital capacity, the venous pressure and the velocity of pulmonary circulation in addition to considering carefully the history and the physical evidence.2It was noted in these studies that an estimation of the pulmonary circulation time was an aid in detecting failure of the right side