2 Gurley transits, circles 51⁄2 inches diameter reading by vernier A to minutes and by vernier B to hundredths of a degree, loaned by Julius K. Monroe. With these transits the line was run from flagpole to flagpole, previously located with the theodolite, in the usual manner with double backsights and foresights. The length of foresight was limited by the length of tape, 500 feet; the length of backsight was limited only by the visibility of the rear tripod. Instead of the ordinary rods for lining in, brass plumb bobs weighing 2 pounds each, supported by tripods 7 feet high, with movable heads were used. As sights were taken on the string supporting the plumb bobs, the line was produced with great accuracy. A brass tack was set in a solid hub at each transit station.

Distances.

Distances were measured to the nearest 1/100 of a foot with a 500 foot standardized steel tape, supported at several points along its length so as to have a uniform slope, approximately parallel to the slope of the ground.

The inclination or slope of the tape was measured by the vertical circle on the transit and the horizontal distance and difference in elevation carefully computed.

Besides the 500 ft. steel tape, which was graduated to single feet, except at each end, where 1 foot was graduated to tenths, a 100 foot steel tape graduated throughout to feet, tenths and hundredths was used for shorter measurements.

Astronomical Observations.

Astronomical observations for azimuth were obtained with the theodolite by observing Polaris near eastern elongation. Ten measurements of the angle between star and mark were made with telescope direct and reversed. in 5 positions of the circle. The mark was a bulls-eye lantern placed at one of the transit stations a mile or more distant, northward. Time was obtained from the railroad; a mean time Waltham watch being compared with 75th meridian time as sent by telegraph from the United States Naval Observatory at Washington each noon, and proper reduction was made for difference in longitude. Azimuth observations were made at 8 stations along the boundary

line, 36.7 miles in length; usually at or near a point of deflection in the final line.

Geodetic Positions.

At a point near Cranesville, West Virginia, 24 miles north of the Fairfax stone and 12 miles south of the Pennsylvania line, connection was made with Piney Swamp triangulation station located by the United States Geological Survey by a belt of triangulation extending westward from Maryland Heights and Sugarloaf, 2 primary triangulation stations of the Coast and Geodetic Survey. The geodetic position of Piney Swamp station is on United States Standard datum, and is thus free from station error. A portion of the boundary line, 1.9 miles east of this station, measured during the progress of the survey, was used as a base line, and by measuring all the angles in 2 triangles accurate connection was made with this triangulation station. From these data the geodetic positions of all large monuments were computed.

Elevations.

The approximate elevations of all stations were determined by carrying a line of vertical angle measurements along the boundary. The elevation of Fairfax Stone was accepted as 3162 feet above mean sea level, as derived from railroad levels, and checks on the heights as computed from this, were obtained at 5 points from the topographic work of the United States Geological Survey, as follows: Near Gnegy Church; at the crossing of the Northwestern Pike; at Hutton; near Cranesville; and at the intersection of the Maryland-West Virginia line with the Pennsylvania state line. The apparent errors at these check points were distributed at the various stations in proportion to the distance.

MONUMENTS.

List of Monuments from the Fairfax Stone to the Pennsylvania Line, Giving the Size, Method of Construction, and Location,-Together with the Latitude and Longitude of Each of the Principal Monuments.

The PRINCIPAL MONUMENTS are uniform in size and shape, and consist of a moulded concrete column,

twenty-two inches square at the base, tapering to ten inches square at four feet in height, (top of mould) and finished, in a few instances, with rounded top, but generally flat, pyramidal shape, extending four to five inches at ove the top of mould, or form, making the entire column four feet four inches in height above base; the corners are beveled one and one half inches in width to prevent defacement.

INSCRIPTIONS: Each Monument, beginning with the initial one at the North Branch of the Potomac River, is numbered consecutively from 1 to 34 Northward to the Pennsylvania State Line; the numbers and the names of the Commissioners being placed upon the south face of the monument, except where set diagonally; the date, 1910, on the North face; the letters MD. on the East, and W. VA. on the West. The letters MD., and W. VA., are 3/4 inches in height and 3/8 inch deep; the numbers 23/4 inches high, and 5/16 inch deep, and the names of Commissioners, one inch in height and of proportional depth. The inscriptions were moulded in the monuments, when built, (except the monument at Fairfax Stone, and Nos. 1 and 2), by means of reversed bevel faced brass and lead pattern letters, which were attached separately to the inside of the "forms"; subsequently the letters MD., W. VA., the names of Commissioners, and the date, 1910, were soldered on plates of tin reinforced with heavy sheet iron, which were securely fastened to the forms with screws. These plates were depressed slightly below the surface, which, on the finished monuments, formed corresponding elevations.

Material.

Three bags (300 pounds) best Portland cement, and seven bags (700 pounds) washed, white sand, were used in each of the large monuments. The cement and sand were thoroughly mixed before and after adding water. This material was firmly tamped in the "form," the top being finished with an ordinary mason's trowel. No stone was used in the monument.

Base.

The base of each of the principal monuments was made of concrete, the usual size being 31⁄2 feet square, and 21⁄2

feet deep, depending upon the character and formation of the ground; in all cases sufficient depth and breadth being obtained to insure stability.

The average amount of material used in each base, was 34 barrel of best Portland cement, 1200 pounds of sand, and 1500 to 2000 pounds of broken stone. The cement and sand were thoroughly mixed before and after adding water; cement and stone were placed in the excavations in alternate layers and the whole thoroughly tamped and bonded. The base was finished and cross-lines indicating its exact center marked upon it, and when firm enough to sustain the weight of the monument, the "form" was set up and carefully centered by means of the cross-lines, and the monument built before the final "set," thus forming the base and column into one solid mass. In the few instances where the bases were built a day or more before the monument, a large stone was set in the center of the base and allowed to project a foot or more above the surface, and the monument built around it, thus securing a firm bond.

Small Monuments.

Small monuments are also of concrete, uniform in size, 1 foot square and 2 feet high, moulded in a wooden form, without taper, and contain 1 bag (100 pounds) cement, 2 bags (200 pounds) washed, white sand. The top was finished in a similar manner to the large monuments. The letters MD cut on the east face, W. VA. on the west, and the date, 1910, on the north. The base, 2 feet square and 2 feet deep, also of concrete, and built as in the larger monuments. One bag of cement and four bags of sand, in addition to the broken stone, were used.

The "Fairfax Stone."

The "Fairfax Stone" stands at the head of the North Branch of the Potomac River. It derived its name from Thomas, Lord Fairfax, who became the proprietor of what was known as the "Northern Neck of Virginia." The original grant was made in 1663, by Charles II of England, and subsequently successively confirmed by James II and George II. The title having rested by

transfers in Lord Fairfax, on the 7th of September, 1736, Commissioners were appointed, with the approval of George II, to define the boundaries of the grant, which was to be "all the land lying and situate between and within the heads of the Rivers Rappahannock and Potomac, the courses of the said rivers together with the rivers themselves." The survey of the upper part of the Potomac River was made in 1736, and at the head spring as then determined a number of trees were marked by the surveyors. A dispute arose between Lord Fairfax and the representatives of the Colony of Virginia as to the source of the Potomac, and no further work or agreement reached until 1746, when representatives for each side having been named, the survey was resumed and a line was run from the head of the Rappahannock to the head of the Potomac River. The trees and springs located in the former survey of 1736, as the head of the Potomac having been found, the course of the trial line was corrected and the final line run in the reverse direction from the Potomac to the Rappahannock.

Before leaving the head of the Potomac, additional trees were marked and a stone set up, described as follows, in the note book (still in existence) of Thomas Lewis, one of the surveyors: "October 23, 1746, Returned to the spring where we made the following marks: on another Beach WB WR 1746 Y3-a stone by the corner pine marked X. on a Beach marked AC." This done we bid FX, adieu to the head spring about 1/2 hour after nine o'clock, our course directing to the head of Rappahannock bearing S. 46° E. 30 poles the top of the mountain in the spring heads on.'

When Lieut. N. Michler made his survey of the meridian line north from the Fairfax Stone in 1859, he thus describes the stone in his report. "The initial point of the work, the Fairfax Stone,-stands on the spot encircled by several small streams flowing from springs about it. It consists of a rough piece of sandstone, indifferent and friable, planted to the depth of a few feet in the ground and rising a foot or more above the surface, shapeless in form, it would scarce attract the attention of the passer by. The finding of it was without difficulty, and its