Note 1 North and South lines are Meridians; East & West parales. [...]

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Marginalia

Inscription Contained Within

A Treatise of Practical Surveying: Which is Demonstrated From its First Principles Wherein Every Thing That is Useful and Curious in that Art, is Fully Considered and Explained, 5th edition

Publication Date of Volume

1789

Location in Volume

Front Free Endpaper

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Description

Note 1 North and South lines are Meridians; East & West parales.

Note 2nd That these rules are only for trigonometry and the bearings are to run from the same point other wise the course came must be reversed in order to make them flow from the same point.

Rules for allowing the variation. If the variation is westerly increasing or easterly decreasing; Run so many Degrees to the right hand of the Course given, as the difference is between the present and former Variations; that is Subtract the Difference in the N,E & S,E; which you must add in the N,E & S,W quarters of the quartered compass. [struck through] Turn to the next page.