Note 21 — Chapter III · THE ILLUMINATING APPARATUS OF LIGHTHOUSES.
Reading edition
From the Greek δίοπτρον, an optical instrument with tube for looking through. Δίοπτρον is from διἁ, through; and ὅπτομαι, I see.
Reading edition
From the Greek δίοπτρον, an optical instrument with tube for looking through. Δίοπτρον is from διἁ, through; and ὅπτομαι, I see.