The instruments used in consulting a chart, i.
"Lectures in Navigation"
Ernest Gallaudet Draper
Long knives are the best instruments-one of fifteen inches and another about ten.
"My Attainment of the Pole"
Frederick A. Cook
I tried to explain to them that the Pole is not visible to the eye, and that its position is located only by a repeated use of the various instruments.
"My Attainment of the Pole"
Frederick A. Cook