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tokens: length. N J can be written as where n 3 is the number density of the gas in units of 1000 cm −3 , 5, t is the turbulent velocity (approximated here as the velocity dispersion of the cloud) in km s −1 , and μ is the mean molecular weight that we will assume to be 2.3 for a gas composed of H 2 and He. The cloud is gravitationally unstable to collapse if N ≥ N J . The volume density can be obtained from Table 2 by taking the average column density, multiplying by the inverse of the OH/H 2 abundance, and dividing by the path length through the cloud. If we assume the cloud extends in the radial direction, the same amount as in the plane of the sky, the path length would be ≈1–4 pc for distances ranging from 400 to 100 pc. In the most extreme low column density case (), n has a value of 34–140 cm −3 . All other values of T ex lead to higher average densities. For these estimates of n, N J ranges from 3.7 to 7.5 × 10 21 cm −2 . The highest column density derivable from the OH data in Table 2 is based on . Using this value and the OH/H 2 abundance leads to an average N (H 2 ) of 1.1 × 10 21 . Even comparing the highest cloud column densities with the lowest values of N J leads to the conclusion that the cloud is not gravitationally collapsing. In this respect, G211+63 resembles the bulk of high-latitude molecular clouds that are not bound by gravity and likely breaking up on the sound crossing time (). If this analysis is confirmed for other IVMCs then these objects may be transient structures formed as thermal instabilities in large-scale atomic flows (e.g. Shore et al. 2003 ; Shore et al. 2007 ; Barriault et al. 2010b ). 5.2 Linewdiths compared to CO Désert et al. ( 1990 ) observed only one position in the cloud (which we refer to as the ‘CO peak’) in the CO(1–0) line. They noted one component with a velocity full width at half-maximum (FWHM) of . They also reported other CO observations but of the (2–1) line from the IRAM 30 m radio telescope that showed two distinct velocity components like the ones we observe for positions 1–3. They give no line parameters but comment that the strength of the two peaks was highly variable within two beams (about 30 arcsec) of the central observation at (l, b ) = (210.927°, 63.280°). They do show a spectrum for the central CO(2-1) position where the two components are each only two channels wide. Their IRAM observations were made at resolution so the individual components have to be less than wide (FWHM). Our OH linewidths are clearly larger than the CO lines in four out of seven instances. The reason for this behaviour is difficult to ascertain because the CO and OH observations are at significantly different sensitivities and resolutions. The behaviour of molecular gas at cloud edges is not often discussed and there is little consensus on even the phenomenology of spectral lines at cloud edges. If the OH main lines are tracing the diffuse outer regions of the molecular cloud, then the broader profiles could be