MAPLE SYRUP AND SUGAR 



383 



nights below the freezing point are considered best in Vermont, and it is 

 current opinion that a temperature of 25 F. during the night and a 

 maximum of 55 F. during the day, with damp, northerly or westerly 

 winds are the conditions under which the best flow is obtained. These 

 changes of temperature cause a certain expansion and contraction of the 

 gases within the cells and intercellular spaces in the wood which results 

 in an alternate pressure and suction. During the sugar season this 

 force varies from a suction of 2 Ib. per square inch at night to a pressure 

 of about 20 Ib. per square inch during the day. 



The commercial flow of sap ordinarily runs from about the middle 

 of March until about the middle of April in the region from Vermont to 

 northern New York, inclusive. In Ohio and western New York the 

 season is usually from late in February to early in April. The beginning 

 of the sap season, of course, is determined wholly by the weather and the 

 latitudes. Records show that the flow has commenced as early as the 

 first of February and as late as the early part of April in the Northeast. 

 The following records were obtained in Ohio from 1880 to 1912 by a sugar 

 grower who kept an actual record of the opening and closing date of each 

 season: 1 



1 No records were taken in this year. 



The longest run on this record is fifty-seven days and the shortest 

 only nine days. The average is thirty-four days. The season ends 



1 See " The Production of Maple Sirup and Sugar," by A. H. Bryan and W. F. Hubbard, 

 Farmers' Bulletin 516, U. S. Dept. of Agriculture, 1912, p. 20. 



