The party under the direction of Captain Talcott left the settlements on Halls Stream on the 6th of September. The main branch of this was followed to its source in a swamp, in which a branch of the St. Francis also had its origin. From this point the party followed the ridge dividing the Atlantic from the St. Lawrence waters until it was supposed that all the branches of Indian Stream had been headed. In this work the party was employed until the 14th September. It had now arrived at a point where the Magalloway River should be found to the left, according to the most authentic map of the country, especially that prepared by the New Hampshire commissioner appointed in 1836 to explore the boundary of that State, and accompanying that report.[90] The party accordingly bore well north to avoid being led from the true “height of land” by the dividing ridge between the Connecticut and Androscoggin rivers. After crossing several small streams, it came on the afternoon of the 15th to a rivulet about 12 feet wide running to the east, which was supposed to be the main Magalloway. The 16th was spent in exploring it to its source. The next day it was discovered that what had been taken for the Magalloway was a tributary of Salmon River, a large branch of the St. Francis, and consequently the party was considerably to the north of the boundary.
The supply of provisions did not allow the party to retrace its steps to the point where it had diverged from the true dividing ridge. The course was therefore changed until it bore a little south; but it was not until the 22d that the party found itself again on the dividing ridge, and then upon the waters of the Magalloway.
The party reached Arnold River, or Chaudiere, above Lake Megantic, on the 24th September. After having recruited and taken a fresh supply of provisions from the depot established there, the party was divided into two detachments. One returned westward to find the corner of the State of New Hampshire as marked by the commission in 1789 appointed to trace the boundary line.
It was there ascertained that the corner was on the true dividing ridge, and not from 8 to 10 miles south, as has been erroneously reported by the surveyor employed by the New Hampshire commissioners in 1836 and reiterated in several official papers. From the State corner the dividing ridge was followed to where it had been previously explored by the party. Thence a course was taken to the northeast so as to reach the head of Lake Megantic, and thence to Lake Magaumac, where on the 8th October the two detachments were again united. The detachment led by the assistant, Mr. Cutts, had successfully followed the dividing ridge from the camp of the 24th on Arnold River to this place.