S78 Queries and Answers. 



Art. V. Queries and Ansivers. 



You are aware, I presume, that immense quantities of sugar are annually 

 made from the juice of the J'cer saccharinum, in the west of Pennsylvania 

 and New York, with which our forests abound (Professor Kid, in his Brhlg- 

 ivater Treatise, says they are " cultivated " !) ; and, as the peculiarities attend- 

 ing the flow of this juice have puzzled me to explain them, I have resolved to 

 state them to you. 1st, It is as completely locked up by continued warmth 

 as by frost, and only flows by the alternate operation of these agents: yet 

 the same degrees of heat, even after frost, have not always the same effect. 

 Thus, a warm south wind stops the flowing more than a cool north-west wind. 

 A bracino- wind promotes the discharge, and a relaxing wind checks it. 2dly, 

 The juice flows for twenty-four hours after a frost; but, when a tapped tree 

 has ceased, tap a new tree, and it will flow considerably, as if a certain quan- 

 tity was discharged by the frost. The juice flows from all sides of the incision. 

 3d. Tap a tree early in the morning, after a cold night, and no juice will flow ; 

 tap it a few hours after, if the day be moderately warm, and the juice will 

 issue in streams. February, and early in March, are the months in which the 

 sugar is made. The people encamp in the woods, and remain there until the 

 trees cease to flow, or they have procured as much as they require. Now, I 

 wish to know, if the saccharine juice be sap, how it happens that a mode- 

 rately cold night is essential to an abundant flow next day ? The farmers told 

 me, "We can do nothing in sugar-making without cold nights." I thought 

 that the sap never flowed until an increase of temperature took place. State 

 the facts in your Magazine, if you please; but give me the explanation by 

 letter, or add it to the article. — M. Philadelphia, March 16, 1837. 



The circumstances attending the flow of sap from the sugar maple of the 

 United States, so accurately detailed by your correspondent at Philadelphia, 

 show, not only what is known from the experience of the manufacturers con- 

 cerning the flow of the juice, but also under what circumstances the flow is 

 more or less copious. 



The movements of the sap of the maple are exactly similar to those of all 

 other trees at the same season, or that are exposed to the same vicissitudes 

 of weather. Why do not trees yield a flow of sap from a wound in summer ? 

 Because every drop absorbed by the roots in that growing season is required 

 to supply the demands of the transpiring bark, leaves, and lengthening shoots, 

 with their flowers or fruit ; so that there is no excess to run out of a wound. 

 And why does the sap not flow in winter ? Because, in that cold season, it is 

 inspissated ; and the pores of the bark are then all naturally sealed. On the 

 return of spring, however, the sap becomes fluid; and as soon as the buds begin 

 to swell, an ascending current commences, and continues during warm 

 weather, and is expended not only in enlarging the buds, but escapes imper- 

 ceptibly and copiously through the porous bark. During this process, should 

 a frosty night or "bracing wind" happen, the pores of the bark are shut up, 

 and the sap accumulates within the vascular membranes ; and if, when so col- 

 lected and pent up, the tree be tapped, an abundant stream will issue out, and 

 continue to run until the surcharge is exhausted, or until a warm state of the 

 air causes a general evaporation of the juices from every other part of the tree, 

 or, lastly, until the flow becomes arrested by frost. 



Thus, the quantity of sap is alternately scanty and copious, according 

 to the temperature of the air, or as the tree has been more or less pre- 

 viously drained during the spring months ; that is, during the period which 

 elapses between the bursting of the buds and the developement of the 

 foliage. 



That sap keeps ascending to, and accumulating on, the recently formed 



. layers of liber and alburnum, when the juices in the bark are congealed by 



frost, may be inferred from what often takes place in America, and other 



