SAP OF SUGAR MAPLE. 185 
water abstracted from the earth by the roots during this season ; 
for all this fluid runs from two or three incisions or auger-holes, 
so narrow as to intercept the current of comparatively few sap 
vessels, and besides, experience shows that large as is the quan- 
tity withdrawn from the circulation, it is relatively too small 
to affect very sensibly the growth of the tree.* The number 
of large maple-trees on an acre is frequently not less than 
fifty, and of course the quantity of moisture abstracted from 
the soil by this tree alone is measured by thousands of gallons 
to the acre. The sugar orchards, as they are called, contain also 
many young maples too small for tapping, and numerous other 
trees—two of which, at least, the black birch, Betula lenta, 
and yellow birch, Betula excelsa, both very common in the same 
climate, are far more abundant in sap than the maple {—are 
scattered among the sugar-trees; for the North American na- 
tive forests are remarkable for the mixture of their crops. 
* Tapping does not check the growth, but does injure the quality of the 
wood of maples. The wood of trees often tapped is lighter and less dense 
than that of trees which have not been tapped, and gives less heat in burning. 
No difference has been observed in the bursting of the buds of tapped and un- 
tapped trees. 
+ Dr. Rush, in a letter to Jefferson, states the number of maples fit for tap- 
ping on an acre at from thirty to fifty. ‘‘ This,” observes my correspondent, 
‘‘is correct with regard to the original growth, which is always more or less 
intermixed with other trees ; but in second growth, composed of maples alone, 
the number greatly exceeds this. J have had the maples on a quarter of an 
acre, which I thought about an average of second-growth ‘maple orchards,’ 
counted. The number was found to be fifty-two, of which thirty-two were 
ten inches or more in diameter, and, of course, large enough to tap. This 
gives two hundred and eight trees to the acre, one hundred and twenty-eight 
of which were of proper size for tapping.” 
{ The correspondent already referred to informs me thata black birch, 
tapped about noon with two incisions, was found the next morning to have 
yielded sixteen gallons. Dr. Williams (History of Vermont, i., p. 91) says: 
‘*A large birch, tapped in the spring, ran at the rate of five gallons an hour 
when first tapped. Hight or nine days after, it was found to run at the rate of 
about two and a half gallons an hour, and at the end of fifteen days the dis- 
charge continued in nearly the same quantity. The sap continued to flow for 
four or five weeks, and it was the opinion of the observers that it must have 
yielded as much as sixty barrels [1,890 gallons].” 
