Note 8 — Chapter II · CONTINUED VOYAGE OF THE TWO SHIPS UNTIL REACHING ICE.[4] MIDDLE OF JULY.
Lewis Page Mercier translation
A glance at the surface is not sufficient to decide the real colour of the water, as it is affected by the reflected colour of the heavens. The influence of the latter must therefore be excluded; and we therefore examined the water through a tube. A convenient arrangement for the purpose offered itself in the opening for hauling in the screw.