New York Weather Bureiau. 437 



kills on the western side and below them on the eastern slide of 

 the river. The river itself has little effect upon temperature dur- 

 ing the winter, since it is frozen over, on an average, from Decem- 

 ber 16th to March 20th at Albany, and is also closed by ice during 

 a portion of the winter below the northern Highlands. Tables 

 showing the dates' of opening and clo&ing of navigation in Lake 

 Champlain and the Hudson river for a long period of years will 

 be found on pages 471, 472. 



The northern portion of the Champlain valley, represented by 

 Plattsburgh, is exposed to the northerly windis of winter, and 

 hence its temperature then differs but little from that of the same 

 latitude of northern New Yotrk generally. The summer tempera- 

 ture lis slightly higher than at any other stations in aiorthern 

 New York, owing to the shelter afforded by the mountains on 

 the eastern and western sides. The annual range is exceeded 

 only by that of Gouverneur. 



The St. Lawrence Valley. 



The long records obtained at Potsdam and Gouverneur prior 

 to 1850 show that at the former station southwesterly winds pre- 

 vail throughout the year and at the latter during all months', ex- 

 cepting November, December and April, when the direction 3s 

 northwesterly. That the winds of the Great Lakes are mainly of 

 the same character has been already shown ; and these find their 

 natural outlet through the channel of the St. Lawrence valley, 

 as will! be made apparent by an inspection of the relief map. 

 Hence, in summer when the southerly component is at a maxi- 

 mum, this section may be included in the region of the Great 

 Lakes, as regards its temperature conditions. In winter there 

 are no( oibstructions to the northwesterly winds from the plains 



