ROBERT GIBSON 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. Dublin: Printed by Oliver Nelson, at Milton’s-Head in Skinner-Row. (2nd ed., 1752); Philadelphia: Printed and sold by Joseph Crukshank in Market-Street between Second and Third-Street (4th ed., 1785)

Robert Gibson wrote what became the American standard survey text during the late 18th and early 19th centuries. Little is known of the author’s life except that he was a teacher of mathematics and possibly died in 1761. The first four editions of his work were published in Dublin, Ireland in 1739, 1752, 1768, and 1777. The first American edition was published in 1785 and is shown as a fourth edition. Later Dublin editions are reported until 1839.

Several changes were made to adapt the book for publication in America. The ones from 1785 to 1808 were by unidentified editors. Later editions were independently revised by three people, D.P. Adams, James Ryan, and John D. Craig. Adams published revised editions in New York in 1811 and 1814. Ryan’s versions were published between 1812 and 1840, first in New York and then in Hartford. Craig’s editions were published in Baltimore between 1816 and 1822. Twenty-four different editions are known to have been published in America.

The first one-third of the book contains instructions in mathematics. Next appears information on linear and square measures, surveying instruments and practice, and determining areas from maps and by calculation. Finally there are brief mathematical tables that include the sun’s declination, conversion of degrees of arc to the quartered compass, and a table giving the difference of latitude and half departure according to the four-pole chain.

The preferred distance-measuring tool is the Gunter’s Chain in either two-pole or four-pole length. The author gives a number of other linear measures used in England and Scotland that call for a different number of feet than the statutory 16½ in a pole. Descriptions then follow for the directional instruments, although none are illustrated. These include the circumferentor, theodolite, semicircle, and plane table. The description of the circumferentor corresponds to that of an early-day plain sighting compass.

The theodolite is non-telescopic, and reported as 10 or 12 inches in diameter with a divided limb. In the middle is fixed a circumferentor, and over it is a moveable index with a pair of sights. The instrument is capable of measuring both angles and magnetic bearings, and instructions for its use describe an innovative technique. First an initial compass bearing is taken, then the circumferentor is removed from the instrument. At subsequent stations the bearings are carried on the divided circle by aligning the circle divisions to correspond with the bearing previously determined for the preceding line. This method has several advantages over compass readings at each station, and eliminates much of the affect of local attraction.

The plane table is said to be about 12 by 15 inches. It is made of three boards which can be disassembled for convenience. When assembled it is enclosed in a box frame which also serves to secure the paper. The outside of the frame is divided in inches and tenths, and the inside in 360°. The degree graduations are centered about a small hole in the center of the plane table board.

Vertical angles are usually measured with a quadrant, although the text provides instructions for holding the circumferentor, semicircle, theodolite, and plane table sideways and using a plumb bob to accomplish this task if necessary.

Nearly one-fourth of the book is devoted to determining the area of land parcels by both drafting and calculating methods. One drafting technique is using a transparent device called a square inch horn for counting the number of square inches in a map plot. The other is to cut out the plotted area and weigh the paper. The calculation methods include examples of dividing the area into a number of triangles and solving each individually. A more sophisticated method is the meridian distance calculation. It is similar to the DMD method used in the 20th century although half-departures are used so there is no dividing the result by two.

The 1785 edition published in Philadelphia adds sections on levelling and the dividing of land, balancing a traverse, and an improved form of area calculation. This uses only one column for the DMD portion of the calculation instead of separating them into north and south elements. The new method saves time by making the mathematics self-checking and survived as the standard DMD calculation into the 20th century. Further additions to the text include a traverse table to the nearest one-quarter degree of angle, and logarithmic tables of both numbers and trigonometric functions. The tables of latitude and half-departure in the earlier editions are omitted in keeping with the new methods of area calculation.

The editions by James Ryan are the only ones to include instrument engravings. On the frontispiece are illustrations of a theodolite, quadrant, and mariner’s compass. The pictured theodolite is telescopic, yet the description in the text still corresponds to the early non-telescopic variety. The result is that some statements in the text are inconsistent with the illustrated item. This oversight and the addition of two primarily nautical instruments suggests that Ryan was more of a marine navigator than surveyor.

The James Craig editions have neither the instrument engravings nor some additional tables that appear in Ryan’s versions. But the Craig edition eliminates the cumbersome 12 to 14 folding plates at the end of the book by incorporating the individual figures within the text. This is not only handier but results in a longer lasting text as the plates are subject to damage from tearing and improper folding.

Gibson’s Surveying was a dominant American text for a half century, and the standard against which others were compared. It appeared on the American scene when there was a need for what it offered, particularly in regard to calculating land areas from metes and bounds surveys. Despite several additions and changes by American editors, it never included descriptions or instructions on newer instruments such as the vernier compass, solar compass, or surveyors transit. Its heyday came and went, and it nobly served the needs of many pioneer American surveyors. Today it continues to serve professional surveyors by providing insight into alternative measuring methods used in early metes and bounds surveys.

Reprinted from P.O.B., Vol. 21, No. 4, March 1996, by permission of Business News Publishing Coompany, Troy, MI.