OF ARTS AND SCIENCES. 39 



i, 500 feet in favorable valleys of southern exposure. In general, 

 it embraces the low area along the coast, a large tongue of low 

 country following the Merrimack and its side valleys, to the 

 sand plains of Lake Winnipesaukee and the valleys which 

 penetrate still farther to the foot of the White Mountains. 

 The bottom lands of the Connecticut are also to be included 

 within the Transition area so far up at least as Lancaster, and 

 Transition species work up the side valleys even to the north 

 side of the White Mountains. The Androscoggin valley also 

 brings Transition forms into the low country to the northeast 

 of these high mountains. In the northern part of the state, 

 the Transition area is limited rather .closely to the flood plains 

 of the rivers and the cleared or settled portions of their banks 

 near at hand, for the sub-Canadian woods here come down to a 

 low altitude. From an examination of the map illustrating the 

 climatology of the state in Hitchcock's Geology of Ne\V Hamp- 

 shire, it is seen that this area coincides in a general way with 

 that included by the summer isotherm of 65 deg. F. as an 

 upper limit, thus showing close agreement with Dr. Merriam's 

 ('98) determination that the isotherm of 64 deg. F. (summer") 

 is the southern limit of the Canadian zone. 



The effect of clearing off the heavy primeval forest by man 

 in his progress up these same valleys has doubtless been to ex- 

 tend in great measure the Transition area. Thus, among the 

 White Mountains, where, within historic times, stood lofty 

 forests on the rich valley floors, are now broad meadows where 

 Bobolinks, Vesper Sparrows, Savanna Sparrows, Red-winged 

 Blackbirds, and less often, Meadowlarks find congenial surround- 

 ings, and Indigo Buntings, Song Sparrows, Field Sparrows, 

 Catbirds, Brown Thrashers, Kingbirds, Least Flycatchers, Bal- 

 timore Orioles and even Wood Thrushes summer in the after 

 growth of bushes, or among the open orchards and shade trees 

 about the farms. As an instance of a species which is even 

 now clearly to be observed thus extending its range, may be 

 noted the Chestnut-sided Warbler (Dendroica pensylvanica} . 

 On several occasions I have found an isolated pair or two of 



