<p><strong>Fig. 8.18. </strong>A chip log, consisting of a weighted board and spool of rope, is used with an hourglass to estimate a ship’s speed.</p>

Fig. 8.18. A chip log, consisting of a weighted board and spool of rope, is used with an hourglass to estimate a ship’s speed.

Image courtesy of Rémi Kaupp, Wikimedia Commons