VerriU.l 260 



He had found that the boundaries between the Canadian and 

 Alleghanian Faunte, as described in a former paper,* are coincident 

 with a line which shall indicate a mean temperature of 50° Farenheit, 

 during the months of April, May, and June. This line commences 

 on the eastern coast, near the mouth of the Penobscot Eiver, in Maine, 

 thence it passes inland curving farther to the east, so as to form the 

 northern boundary of the belt of coast-land along the shores of the 

 Bay of Fundy, which is characterized by forests of coniferous trees, 

 but smaller in size than in Northern Maine. The low temperature 

 of this region is evidently caused by the influence of the cold waters 

 of the Arctic current, which sweeps along the coast, producing 

 even in mid-summer, cold fogs, whenever southern winds prevail; 

 the influence of these fogs and cold south winds diminishing in 

 going inland from the coast. The meterological data at his com- 

 mand were insufficient to determine whether the line of 50° extends 

 into central New Brunswick, which is, however, quite probable. 

 After reaching its eastern limits in the interior, the line turns to 

 the westward so as to enclose a narrow belt of country reaching as far 

 northward as the southern part of Aroostook County in favorable 

 localities, and bounded on the north by the coniferous forests of North- 

 ern Maine. It passes south of Moosehead and Umbagog Lakes, but 

 rises somewhat northward along the Androscoggin Valley, thence it 

 passes southward of the White Mountains, through the vicinity of 

 Conway, N. H. It bends northward again up the Connecticut Valley 

 as far as Craftsbury, Vt., where the mean temperature is 50° 91. It 

 turns to the southward again along the eastern slope of the Green 

 Mountains, the higher portions of which, even in Western Massachu- 

 setts, and perhaps in Connecticut, have a temperature below 50°. 

 West of the Green Mountains it suddenly bends far to the north, 

 along the Champlain Valley, and thence to the valley of the St. 

 Lawrence, as far at least as Montreal, then following the river, it appar- 

 ently extends to Lake Ontario. The Adirondack region is skirted on the 

 eastern side along the shore of Lake Champlain by a branch of this line, 

 which, passing to the south of this extensive mountain region, unites 

 with the northern branch, thus leaving the entire Adirondack region as 

 an island of the Canadian Fauna, surrounded by the Alleghanian, just 

 as, geologically, it is an island of azoic, granitic rocks, surrounded by 

 the Silurian limestones, sandstones, and slates, which form the low 

 lands on all sides, resting against the flanks of the mountains, and 

 extending inward along the river valleys. The line appears to cross 

 Lake Ontario and the southern part of Lower Canada, entering 

 Michigan in the vicinity of St. Clair. It crosses the northern part 

 of Wisconsin north of Milwaukee, and then bends northward up the 



* rroceediugs of the Essex Institute. Vol. Ill, p. 136. 



