Speculum nauticum a looking glasse for sea-men : wherein they may behold a small instrument called the plain scale whereby all questions nautical and propositions astronomical are very easily and demonstratively wrought ... / by Iohn Aspley.

CHAP. XI.

To finde the distance of any Island from you, that you may discerne by two Stations, knowing the point of the Compasse, the Island beareth unto each of the Stations.

Suppose (being at Sea) you discover an Island bearing South-west of you, which place let it be your first Sta∣tion, and seventy Leagues sayling South observing the Island to beare West of you, which let be the se∣cond Station, the demand is to finde the Island from both the Stations.

IN the second Demonstration let A, be the first Station, and upon the Centre A, draw the quadrant A B D E, then in regard you found the Island to beare South-west from you, therfore take four of your eight points of Com∣passe, and place them upon your Quadrant from E, unto D, then from the Centre A,

by the point D, draw the Line A D F, representing the visuall Line passing betwixt your sight and the Island, being in the first Station. Then sayling seventy leagues South, which is from A, your first Station, unto C, the second Station: then observing the Is∣land to beare West of you, therefore from the point C, the second Station, draw the Line

[illustration]

dem: 2

C F, parallell unto A E, cutting the Line A D E, in point F, so shall the point F, be the place of the Island desired, and the distance A F, is the distance of the Island from the first Station, which is just ninety nine Leagues off the Line of equall parts. And likewise the distance from C, unto F, is the distance of the Is∣land from the second Station, which is here found to be just seventy Leagues: and by this manner of worke you may finde the distance of any Island from you, which you may discerne either by Sea or Land.