For reference (and for correction in future printings):
The Teacher's Notes for Week 21, pp.52-53, seem to have two separate incidents in Hudson Taylor's life combined as if they were one. The incident in Ning Po, related to the Arrow, is on pp.136-138 in the book. The incident when the mission building was looted and only one room spared was in Yang-Chow, related in the book, pp. 185-193. God protected them in both cases, so the point is the same.

It'd be good if there were a correction page posted for those receiving the printed version (which I suspect is past revising for this printing). Thanks!