Throughout this voyage we were struck by the rarity of some sorts of animals and the continual remarks that three, five, or six years ago these same sorts were extremely abundant; and in some few cases the conditions were reversed. For example, during a week spent at Fort Smith, Preble had out a line of 50 mouse-traps every night and caught only one Shrew and one Meadowmouse in the week. Four years before he had trapped on exactly the same ground, catching 30 or 40 Meadowmice every night. Again, in 1904 it was possible to see 100 Muskrats any fine evening. In 1907, though continually on the lookout, I saw less than a score in six months. Redsquirrels varied in the same way. Of course, the Rabbits themselves were the extreme case, millions in 1904, none at all in 1907. The present, then, was a year of low ebb. The first task was to determine whether this related to all mammalian life. Apparently not, because Deermice, Lynxes, Beaver, and Caribou were abundant. Yet these are not their maximum years; the accounts show them to have been so much more numerous last year. There is only one continuous statistical record of the abundance of animals, that is the returns of the fur trade. These have been kept for over 200 years, and if we begin after the whole continent was covered by fur-traders, they are an accurate gauge of the abundance of each species. Obviously, this must be so, for the whole country is trapped over every year, all the furs are marketed, most of them through the Hudson's Bay Company, and whatever falls into other hands is about the same percentage each year, therefore the H. B. Co. returns are an accurate gauge of the relative rise and fall of the population. Through the courtesy of its officials I have secured the Company's returns for the 85 years--1821-1905 inclusive. I take 1821 as the starting-point, as that was the first year when the whole region was covered by the Hudson's Bay Company to the exclusion of all important rivals. First, I have given these accounts graphic tabulation, and at once many interesting facts are presented to the eye. The Rabbit line prior to 1845 is not reliable. Its subsequent close coincidence with that of Lynx, Marten, Skunk, and Fox is evidently cause and effect. The Mink coincides fairly well with Skunk and Marten. The Muskrat's variation probably has relation chiefly to the amount of water, which, as is well known, is cyclic in the north-West. The general resemblance of Beaver and Otter lines may not mean anything. If, as said, the Otter occasionally preys on the Beaver, these lines should in some degree correspond. The Wolf line does not manifest any special relationship and seems to be in a class by itself. The great destruction from 1840 to 1870 was probably due to strychnine, newly introduced about then.