Intensity and LOS velocities of the H 39−44α transitions observed at the positions of the clumps in the Lagoon Nebula. The fillings of the coloured dots indicate the intensities and the borders describe the velocities. Blue and green stars respectively mark the positions of present O- and B-type stars. The grey-scale background image shows the JCMT SCUBA 870 µm dust continuum flux (see Fig. 2).