On Hearne's first and second journeys he had quite adequate scientific apparatus, and so could take astronomical observations to determine his true position. So we find that he occasionally made use of his quadrant and took such observations; consequently the positions given on the map for the principal points in these two journeys are approximately correct. But he started on his third journey with very faulty instruments, and he would appear to have made very little use even of them. The map of the course followed by him on this journey strongly suggests a rough sketch made by his Indian guide, rather than a careful plan worked out by himself, from day to day, or week to week. For example, between Island and Kasba Lakes, near the beginning of his journey, and shortly after he had diverged from his course of the previous year, he began to go wrong. If he was using his compass at all, it is possible that some source of local magnetic attraction was influencing it, for the position of the last-named lake (on his map) is some sixty or seventy miles too far north. It is inconceivable that he could have made any serious effort to correct this faulty course by astronomical observations with his quadrant. His book is chiefly valuable therefore not so much because of its geographical information, but because it is an accurate, sympathetic, and patently truthful record of life among the Chipewyan Indians at that time. Their habits, customs, and general mode of life, however disagreeable or repulsive, are recorded in detail, and the book will consequently always remain a classic in American ethnology.
The manuscript report on Hearne's exploration was submitted to the directors of the Hudson's Bay Company immediately after his return, and they highly commended him for the work he had done, and gave him a handsome bonus.[10] The first account of his journey which seems to have been published was given to the world in 1784 in the "Introduction to Cook's Third Voyage," pp. xlvi-l, written by Dr. John Douglas, Bishop of Salisbury, who later also edited Hearne's own book. The route followed by Hearne on his successful third journey is incorporated in the general map of the world accompanying this book. A Mr. Roberts, who prepared this map, makes the following note with regard to it:—
"The whole of Hudson's Bay I took from a chart compiled by Mr. Marley, from all the most authentic maps he could procure of those parts, with which I was favoured by Samuel Wegg, Esq., F.R.S., and Governor of that Company, who also politely furnished me with Mr. Hearne's Journals and the map of his route to the Coppermine River, which is faithfully inserted in the chart.
"(Sgd.) Henry Roberts.
"Shoreham, Sussex, May 18, 1784."[11]
Another brief account of Hearne's trip is given in "Pennant's Arctic Zoology," also published in 1784, while his map is incorporated in one of the maps published in "Pennant's Supplement to Arctic Zoology," 1787. Some of the names used on these two maps were continued on the map accompanying Alexander Mackenzie's "Voyages," and also on Arrowsmith's maps up to comparatively recent dates.
The book here republished appeared first in 1795, three years after Hearne's death, as a large quarto volume of xliv + 458 pages, with five maps, and four full-page illustrations. It was edited by the above-named Dr. John Douglas, who is said to have drawn up the narrative, and to have finished the Introduction, though just how much Hearne's diction was altered by the editor is not known. It is probable, however, that the MS. was published almost exactly as Hearne had written it. An octavo edition, similar in letterpress to the original quarto one, but with some slight omissions or differences in the text and in the general map, was published in Dublin in 1796.