. First page Back Continue Last page Summary Graphics . Rosette MC (Williams et al. 1995) . HISA 0 physically associated with MC . HI excess emission in the same velocity range . 0 N(HI) ~(0.6-1.3) 1021 cm-2 , <n(HI)>=1.7-9 cm-3 . The argument by Williams et al is little bit different. They found HISA associated with some limited areas of RMC. Then they used the HI emission at the same velocity interval to derive a mean density between 1.7 and 9.