The red symbols mark the location of observations recorded in ship logbooks.
The Reading Room's high-ceilinged space is filled with nautical bric-a-brac: photographs of bearded men smoking pipes, with nicknames like Slooper, Brushy and Jimbo; a notice from 1732 declaring the amount sea widows could receive in pension; figureheads of fair maidens; ship logbooks and models; drawings and poems.
Observations are found in many documentary sources, including old books, periodicals and journals, ship logbooks, in experimental medical and scientific research, military reports and records, newspapers, and diaries.
Comprehensive datasets further incorporating measurements reported in ship logbooks by mariners during their navigation around the world have been used to construct global geomagnetic field models encompassing the past four centuries, in the form of Gauss coefficient time series.
In addition, one should not forget the Dutch, Portuguese and Spanish ship logbooks, as their vessels continued to sail to their colonies long after the dominance of their empires that ruled them had faded.c From the 1790s, barometer and thermometer readings were entered as standard practice in English logbooks.
The English East India Company (EEIC) ship logbooks, for example, which contain excellent weather observations from at least the 1780s, are also full of narratives of a vessel's several year voyage and include detailed descriptions of the crew and their lives aboard ship, as well as the lands to which they travelled.
"Today's mapping of geomagnetic variations back to 1590 is the fruit of the collaboration between historians and mathematicians — gathering magnetic observations in ship logbooks, blending them with observatory data, available mainly after 1840," he said.
To deduce this fact, the group used ships' logbooks from the period that recorded the direction of the magnetic-field lines at the Earth's surface for the purpose of navigation.
It was written in pencil in an old ship's logbook, and I didn't even bother typing it up; I'd already decided it was juvenilia.
