Suppose a Ship to make a Voyage Eastward from a Place in Lat: 40. North, to a Place in Lat 50. North, Distance in Longtitude 75 Degrees.

In sailing from 40 to 50 she goes from a Place where a Degree of Longtitude is about 8 miles greater than in the Place she is going to. A Degree is equal to 4 Minutes of Time. Consequently the Ship in the Harbour she leaves partaking of the Diurnal Motion of the Earth, moves two miles in a minute faster, than when in the Port she is going to; which is 120 miles in an Hour.

This motion in a Ship and Cargo is of great force; and if she could be lifted up suddenly from the Harbour in which she lay quiet, and set down instantly in the Latitude of the Port she was bound to, tho’ in a Calm, that Force contained in her would make her run a great Way at a Prodigious Rate. This Force must be lost gradually in her Voyage, by gradual Impulse against the water, and probably thence shorten the Voyage. In returning just the contrary must happen and her Voyage be retarded and lengthned.