Abstract: | The mass loss of T Tauri stars leads to the production of dust in circumstellar space. The total amount of lost mass (and therefore of produced dust) is observed to be positiv correlated with the intensity of the H and Call emission lines of the objects. This fact is used in the present paper to explain quantitatively another correlation, namely the observation, that the interstellar extinction which is found by star counts in the wider surroundings of a T Tauri star is roughly proportional to the intensity of its Hα emission. By this, the outflow of circumstellar matter into the interstellar space seems to be observable directly. |