ing, and the signing of the official maps by the commissioners, the engraved copper plates should be deposited in fireproof vaults for safe-keeping.

X. That the field work of retracing, locating, mapping, and monumenting the boundary should be divided, in approximately equal amounts, between the two sections of the commission, as follows:

All the work, except the main scheme triangulation, from the St. Croix River to the St. John River and along the St. John River to the St. Francis River to be allotted in general to joint parties of United States and Canadian surveyors, and similar work along the lower half of the St. Francis River to United States surveyors, and along the upper half of the river to Canadian surveyors; and the main scheme triangulation, furnishing the major control for the above work from the source of the St. Croix River to Lake Pohenagamook, to Canadian surveyors.

All the field work, except the monumenting, from Lake Pohenagamook along the Southwest Line to monument 187, and from monument 222 to English Lake, and thence along the South Line to the Southwest Branch of the St. John River, to surveyors of the United States section of the commission; and all the monumenting along the Southwest Line and the South Line, from Lake Pohenagamook to the Southwest Branch of the St. John River, and all the other field work from monument 187 to monument 222 on the Southwest Line, to surveyors of the Canadian section. All the field work on the boundary along the Southwest Branch of the St. John River and on the boundary along the Highlands from the Southwest Branch of the St. John River southwestward to monument 402, the point where the Canadian Pacific Railway crosses the boundary, to be surveyed by Canadian parties; and all the work on the boundary along the Highlands westward from monument 402 to the head of Halls Stream and along Halls Stream to the "Valentine and Collins" line to be allotted to United States surveyors.

The main scheme triangulation along the Vermont-Quebec line westward from Halls Stream to the Richelieu River, to control the retracement, monumenting, and mapping of the boundary done jointly by the United States and Canadian surveyors under the joint and concurrent action of the two Governments in 1906 and 1907, to be done by Canadian surveyors.

The work of making a topographic map of the country adjacent to the boundary from the Richelieu River to the St. Lawrence River to be done by surveyors of the United States section, and the field work of tying the traverse of this line to the primary triangulation of the Geodetic Survey of Canada to be done by Canadian

surveyors.

XI. That, along Halls Stream, the Southwest Branch of the St. John River, and the St. Francis River where the beds of the streams have been changed in certain places by avulsion since the boundary line was laid down in 1845, in order to "reestablish the location of the said boundary" in accordance with the provision of Article III of the treaty of 1908, specifying that the course of the entire boundary should be marked by said commissioners as described in Article I of the treaty of 1842 and as laid down as aforesaid under Article VI of that treaty, the line should be relocated along the old bed of the stream as shown on the maps prepared under the treaty of 1842, and not along the new channels which have been formed since then.

RETRACEMENT OF THE BOUNDARY LINE

Before the work of locating, remonumenting, and mapping any section of the boundary could be undertaken, it was necessary to identify on the ground the line as laid down under the provisions of the treaty of August 9, 1842.3

The character of this work varied according to conditions. Along the Highlands, the work consisted of running out the line between monuments in accordance with the old notes, or, where the notes were obviously in error, by following the crest of the watershed or traces of the old vista. On straight-line sections of the boundary, dependence was placed chiefly upon the location of important monuments, the operations consisting of searching for and finding the monuments and determining whether any of them had been moved from their original sites. Where the boundary followed watercourses, and no old notes were available and but few monuments had originally been set, the course of the line was taken entirely from the original boundary maps, the chief problem being to determine in each case whether the channel of the stream had been changed by avulsion since the treaty of 1842, as, for example, on parts of Halls Stream, and in such case to find the bed of the original channel, which, as agreed by the commissioners, was to determine the final location of the line.

3 The details of the work of retracement are given in the chapters on "Field operations," Description of field methods," and "Description of office methods."

THE NORTH LINE

The retracement of this portion of the boundary, from the source of the St. Croix River northward 78 miles to the St. John River, was made from the survey notes of 1843, accepting as fixed points on the boundary those monuments which were found not to have been moved. A vista was cleared between monuments where necessary, and the line run out and measured. The distances between monuments, and the 25 deflections in the line, averaging about 12 minutes of arc, were found to agree closely with the measurements made during the survey of 1843. One hundred and six of the old boundary monuments were found on their original sites, and eleven monuments were found to have been displaced and were later restored to the line by the monumenting party, only one, however, being placed in its original position.*

THE BOUNDARY ALONG THE ST. JOHN RIVER

The records of the original survey of the boundary through the St. John River, made under the treaty of 1842,

consist of a set of general maps showing the islands and shore line of the river, the boundary, the mouths of tributary streams, and a few roads and buildings, on a scale of 4 inches to the mile, and a set of detail maps showing the soundings between the islands and the mainland, on a scale of 12 inches to the mile. The maps showed that 60 cast-iron monuments had been placed on the islands in the river to indicate their nationality, but no records or notes of the old survey could be found to show the exact relation of the monuments to the boundary or to the shore lines of the river. The original location of the boundary had to be determined, therefore, solely by its position as shown on the maps in relation to the topography of the adjacent islands and

streams.

The work, therefore, of retracing the line along the river included making an accurate topographic map and comparing this map with the old maps to determine

Special type of cast-iron monument, as reset at source of St. Croix River

See chapter "Monuments and monumenting," p. 107.

what changes had occurred in the shore lines of the river and islands since 1843, and then drawing on the new map a series of straight-line courses conforming as nearly as practicable to the course of the curved boundary shown on the original maps. It was agreed by the commissioners that this series of connecting straight lines should be tied to reference monuments set on the river banks and islands, and should constitute the final location of the boundary.

THE BOUNDARY ALONG THE ST. FRANCIS RIVER

The retracement of the boundary along the St. Francis River presented the same problem as that on the St. John River. No notes of the original survey were available, but the old commission maps of 1843 showed this part of the boundary as a curved line following the channel of the stream.

A new topographic map was made and the course of the stream was compared with that shown on the old maps. It was quite evident from this comparison that at some places there had been a gradual shifting of the channel, due to the swift current cutting away the banks at sharp bends and building up sand bars, and that at two places the stream had been changed by avulsion.

At the places where the change in the river had been gradual and due to erosion and accretion, the boundary was placed as near the center of the present channel as practicable, and at the two places where the stream had abruptly left the old channel the line was laid down along the course of the old channel, which was well defined and easily identified. Throughout its entire course, the new boundary consists of a series of connecting straight lines conforming as closely as practicable to the curved line shown on the old maps.

THE SOUTHWEST AND SOUTH LINES

The Southwest and South Lines, comprising the section of boundary from Lake Pohenagamook to the Southwest Branch of the St. John River, as surveyed under the treaty of 1842, consisted of two lines, intersecting near the southern end of English Lake and having a combined length of 84 miles, along which there had been set 131 cast-iron monuments, fairly uniformly distributed. The records of the original survey consisted of the old commission maps and survey notes which gave the distances between monuments and the results of astronomical observations, determining the azimuths of the lines.

The boundary was retraced by clearing a vista between monuments and running a precise traverse with theodolite and invar tape in accordance with the original notes. The direction of the line was verified by observing an astronomical azimuth at a station on the boundary at Lake Pohenagamook. The results of this observation differed from the azimuth of the line as observed in 1843-44 by only 4 seconds of arc. The precise traverse of the Southwest Line and the South Line developed the fact that sections of the monumented line running between prominent intervisible points deviated slightly from the two major straight lines indicated by the old notes.

old monuments except four were found in place and were reset in concrete bases to make the line conform as closely as possible to the original straight-line locations indicated by the precise traverse.

THE BOUNDARY ALONG THE SOUTHWEST BRANCH OF THE ST. JOHN RIVER

The original records consist of a set of maps made during the survey under the treaty of 1842, upon which are shown the river with the boundary midway between its banks, also the tributary brooks and the five monuments set in 1845.

The retracement of this part of the line was accomplished by making an accurate topographic map of the stream and comparing its course with that shown on the maps made in 1844-45. This comparison indicated that, with one exception, only a few minor changes in the position of the stream had taken place due to erosion and accretion. Accordingly, the boundary was laid down as a series of straight lines following the center of the present channel as closely as practicable, except at the one place where the stream had abruptly left the old channel, where it was laid down along the course of the old channel, which was well defined and easily identified. The boundary throughout was made to conform as nearly as practicable to the curved boundary shown on the old maps. Because of the narrowness of the stream this was done in the field instead of by scaling from the map as was done in the case of the St. John River. The position of the line was fixed by permanent reference monuments established along the banks.

THE BOUNDARY ALONG THE HIGHLANDS

The Highlands boundary, which extends from a point near Little St. John Lake at the source of the Southwest Branch of the St. John River to the head of Halls Stream, a distance of 175 miles, follows the crest of the watershed which separates the headwaters of the Penobscot, Kennebec, Androscoggin, and Connecticut Rivers from the waters which flow into the St. Lawrence River. The course of this part of the boundary is very tortuous. As established under the treaty of 1842, it was marked by a vista and by 192 cast-iron monuments and 2 wooden monuments fairly uniformly distributed along the boundary. The records of the original survey include maps of the boundary and notes of two independent traverses run along the crest of the divide by British and United States parties, respectively, in 1844-45. The deflection points of neither of these traverses were permanently

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