. The Canadian field-naturalist. May, 1934J The Canadian Field-Naturalist 75 valuable manner and between them cover most of the inliabited regions of Canada south of the tree limit and north of the prairie. A number of reperts do, in fact, cover a further portion of the settled belts in which rabbits are scarce or absent: these have been omitted from the present analysis. In map- ping- the Hudson's Bay Company results a conventional area of fifty miles radius (a circle a lumdred miles across) was allotted to each post, following the advice of the com- pany's officials. In most instances this i
. The Canadian field-naturalist. May, 1934J The Canadian Field-Naturalist 75 valuable manner and between them cover most of the inliabited regions of Canada south of the tree limit and north of the prairie. A number of reperts do, in fact, cover a further portion of the settled belts in which rabbits are scarce or absent: these have been omitted from the present analysis. In map- ping- the Hudson's Bay Company results a conventional area of fifty miles radius (a circle a lumdred miles across) was allotted to each post, following the advice of the com- pany's officials. In most instances this is admitted to be an underestimate. The in- formation is supplied by the post manager, on the basis of his own observations and those of trappers and other visitors to the post. Where overlapping occurs between neighbour- ing posts, any difference in record is mapped by dividing the territories in a simple geomet- rical manner. In future years it will be pos- sible to obtain more precise information about the exact regions to which observations for each post refer. It was considered advisable to try to es- timate the degree to which the grid system does exaggerate the actual area of ground covered by observers, who do not, of course, form a completely overlapping system of "ter- ; This was done by measuring the actual original areas plotted on the large scale maps of the provinces, by means of an Amsler planimeter. The technique is a good deal more laborious than the grid method but the results have a high degree of accuracy— much higher than the actual plotting of areas from observers' descriptions. Only the National Parks were examined in this way. In carrying out this special test I wish to acknowledge the assistance kindly given by Mrs. M. J. Baden-Powell who also copied a number of large scale tracings for the Bureau. Prince Edward Island was omitted owing to in- sufficient data. The total area covered by the National Parks results was for the grid abou
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