Imaging of the respiratory system developed with exceptional rapidity in North America during the spring of 1896, after Roentgen's discovery of X-rays in November 1895, largely because of the efforts of a unique physicians, Francis H. Williams. With great zeal, this pioneer used fluoroscopy for early detection of tuberculosis and other life-threatening chest disorders. By the summer of 1896, he had accumulated more than 100 volumes containing tracings of clinical chest fluoroscopy. As a result of his extensive clinical experience, his dedication to patients' welfare, and his sense of scientific inquiry, several inventions and many landmark clinical observations were made in the first few years after the discovery of the X-ray. These included (1) the invention of a "densitometer" for standardized measurements of relative X-ray attenuation of the lung, (2) the invention of a "seehear" device to correlate auscultative findings and fluoroscopic observations, (3) the recognition that fluoroscopy was more accurate than percussion for estimating mediastinal displacement, (4) the discovery that clinically occult tuberculosis and congestive heart failure could be detected with fluoroscopy, (5) the documentation that unilateral chest disease caused decreased ipsilateral ventilatory compliance and increased contralateral ventilation, (6) the identification of the classical imaging characteristics of tuberculosis, pneumonia, pneumothorax, tension pneumothorax, pleural effusion, hydropneumothorax, emphysema, congestive heart failure, and air trapping. In April 1896, Dr. Williams described the "air bronchogram" in a radiograph of a patient with pneumonia.