The interstellar clouds of Adams and Blaauw revisited: An HI absorption study - I

This investigation is aimed at clarifying the nature of the interstellar ga s seen in absorption against bright O and B stars. Towards this end we have obtained for the first time HI absorption spectra towards radio sources ve ry close to the lines of sight towards twenty five bright stars previously studied. In this paper we describe the selection criteria, the details rega rding our observations, and finally present the absorption spectra, In the accompanying paper we analyse the results and draw conclusions.