peaks (e.g. Prinja et al. 2005) and Si$^{3+}$ may be expected to be dominant. However, the spectra of both stars have Si [iii]{}$\lambda1206$ and C [ iv]{}$\lambda\lambda 1550$ wind lines that are unsaturated at intermediate velocities and have saturated NACs. Combining the relative oscillator strengths and adunances of these lines suggests that Si [iii]{}$\lambda1206$ and C [iv]{}$\lambda\lambda 1550$ would be 2.8 and 3.9 times stronger (respectively) than Si [iv]{}$\lambda\lambda 
1400$ for the same column density of wind material. Thus, it is possible that no more than $\sim 1/3$ of the silicon is in Si$^{3+}$ and that even though $q($Si$^{3+})$ in the NACs of these stars are only $\sim 0.01$ $\dot{M}({\rm Vink})$ (Table 3), the actual mass loss rates could easily be 3 times larger. However, that is still a factor of 30 below theoretical expectations.

The UV mass-loss diagnostics discussed here can have wider applications in the (majority) cases where the resonance line doublets cannot be treated as radiatively decoupled. We can adopt the B supergiant results derived here and model just the blueward NAC in any well-defined OB star unsaturated P Cygni profile. This is feasible with our methods because we are fitting the outer region of the wind 