Illustration of the physical picture that explains (to zeroth order) the features seen in the drift velocity in Fig. 1 at two different times during the evolution of the cloud. Color-coded tubes represent magnetic field lines, green arrows show the direction of the magnetic tension force per unit volume, and orange arrows show the direction of the neutralion drift velocity. On the left side of the plot we depict the situation at one free-fall time, when magnetic-field lines have approximately an hourglass morphology. The right side of the plot shows the evolved magnetic-field morphology (at 1.44 t_ff), which explains the anticorre-lation seen in the neutral-ion drift velocity with respect to the midplane of the cloud.