The vexed question of wind direction
Wind direction is the most commonly recorded of all weather elements in nautical logbooks, and was noted several times each day. The convention of describing wind by the direction from which it was coming (rather than the direction towards it was blowing) had been established during the 16th century and persists to the present day.
The directions were described using a 32-point compass (as illustrated) and could thus be written as N, E, S or W (initials were nearly always preferred for brevity), or as SE, SbW etc. depending upon prevailing conditions. For scientific purposes such directions can if necessary, be easily converted to degrees from north.
It might be thought therefore, that of all the various logbook weather entries, wind direction would be the least ambiguous. Surprisingly this is was not the case, and some effort was expended in determining if the directions were with respect to 'true' or to 'magnetic' north. The two are different and to make matters more complicated the difference, or variation as it is known, changes over space and time. It may be zero, in which case true and magnetic north coincide. On the other hand and especially in the high latitudes, it can be over 25° in either direction.
The logbooks give no indication of the convention that was used when recording wind direction relative to the true or magnetic pole. But the question had to be resolved as the scientific application of the data required that they be with respect to true north. Studies of contemporary 18th and 19th century publications on navigation clearly indicated that the recorded directions were 'magnetic', and that corrections to 'true' courses that could be plotted on the sea charts of the time were made only at the conclusion of the arithmetical calculations required by dead reckoning and other procedures.