During the days when ships were powered by sail, the captains
log documented everything that happended during the
day. As sickness could spread rapidly on a ship,there were often times where the number of sailers that were
ill exceeded the space provided in the
log to record their names. During these times, the excess names of the sick were recorded in the next column, which was reserved for the weather conditions of the
day. Thus, it was not unusal for an ill sailor to be listed "under the weather".