Hello,
thanks for the pictures, and the report, the book you photographed is the manual (from 1775) of the “GPS” you are referring to a bit later in your report, the page you pictured says :
or method to determine longitudes at sea, with the help of marine clocks.
Followed by the collection of the tables useful to the pilot to reduce (use? conclude from ?) the observations relating to longitude and the latitude.
By Mr. Ferdinand Berthoud, mechanic clockmaker of the King
and of the Marine, in charge of the inspection of the construction of the marine Clocks, and member of the Royal Society of London.
Best