JAMES STEVENSON / SCIENCE PHOTO LIBRARY JAMES STEVENSON / SCIENCE PHOTO LIBRARY
A thermohydrograph in its protective case. This is an instrument for making local temperature and relative humidity measurements of the air. It consists of a metal-ring thermometer (top) and a hygrometer. Both instruments leave traces on a slowly-rotating recording barrel at left; the barrel is fitted with a chart that can record a whole week of data. The slots in the case at right allow natural air circulation to prevent artificial 'greenhouse' warming inside the transparent box, but also act as a baffle against stronger air movements. The readings shown here are approximately 19 Celsius and 45% relative humidity.
Model release not required. Property release not required.