The height of the stationary camp at Mount Biort having been determined by observations continued for several days, the level of Lake Temiscouata was thence determined by using a set of levels taken with a theodolite by Breithaupt, of Cassel, in 1840.  The height of the lake thus deduced is greater than it would appear to be from the barometric observations taken in December, 1840.  It had been imagined that a difference in level might exist between the St. Lawrence at Metis and at the river Du Loup.  Four days of contemporaneous observations were therefore made at each with a view to the solution of this question.  The idea of a difference of level was not sustained by the operation.

The heights of the river stations were measured in each case to the highest mark left by spring tides, and half the fall of that tide as given by Captain Byfield has been added in all cases as a reduction to the mean level of the sea.  Opportunities were offered in a few instances for testing the accuracy of the method by different barometers used by different observers at different days on the same point.  No discrepancy greater than 7 feet has been thus discovered.  In other cases the same observer returned and observed at the same places, and here a similar congruity of result has been found to exist.

The whole of the calculations have been made by the formulae and tables of Bailey.  Before adopting these their results were compared in one or two instances with those of a more exact formula.  The differences, however, were found so small as to be of no importance, amounting in the height of Lake Johnson to no more than 5 feet in 1,007.  The original record of the barometric observations, each verified by the initials of the observer, have been deposited in the State Department.

25.  The paths pursued by the traveling parties were marked by blazing trees.  The position of the barometer at each place of observation was also marked.  The operation was a search for the boundary line in an unknown country, hence it rarely happened that the path of the parties has pursued the exact dividing line of the waters of the St. Lawrence and the Atlantic, but has been continually crossing it.  The maps herewith submitted and the marks by which the line of the survey has been perpetuated would have enabled a party sent out for that especial purpose to trace the boundary on the ground without difficulty other than that arising from the inacessible character of the country.

26.  The commissioner can not speak in too high terms of the industry and perseverance manifested by the engineers and surveyors employed on this division, and in particular of the skill and intelligence of the two first assistants.  Circumstances had prevented the receipt of portable astronomic instruments which had been ordered from Paris and Munich, and an instrument formed by the adaptation of a vertical circle to the lower part of an excellent German theodolite by Draper,