Eudiometer, one of three of different designs, said to have been used by M. Berthelot

A eudiometer is designed to test the oxygen content of the air and is used today in chemistry. Atmospheric air and hydrogen are exploded over water by an electric spark and the rise in the water in the tube gives an indication to the amount of oxygen present. Eudiometers were taken across Europe by tour organisers looking for the best places for health resorts. Disease was thought to be caused by bad air and foul smells as a result of rotten rubbish, human waste and stagnant water. So clean air was considered essential in treating and preventing illness. The eudiometer is photographed with another one of similar design (1984-1261/1).