XXXII. THE ROCK MAPLE. 493 
lindens, the hickories and the walnuts, is watery and sweet, 
and contains crystallizable sugar; but none so abundantly as 
that of the Sugar Maple. 
The Sugar Maple should not be tapped before it is twenty-five 
or thirty years old; but the process may be repeated annually 
as long as the tree lives. Some trees have been tapped for more 
than forty successive years without apparent injury. Other 
trees have had their growth retarded by it. This is probably 
more owing to the wound necessarily inflicted, than to the loss 
of the sap, as it is found that the quantity and quality of the 
sap yielded are visibly improved after the first tappings. ‘The 
quality varies with the situation of the tree. In the forest, sur- 
rounded. by other trees, and having comparatively few branches 
and leaves, a tree yields but one pound of sugar for five or six 
gallons of sap; when growing in the open ground, where it is 
exposed to the action of the sun through the year, a tree yields 
a pound from four and sometimes even from three gallons. The 
average quantity is from twelve to twenty-four gallons each 
season. In some instances itis much greater. A gentleman* 
of Bernardston informs me that a tree in that town about six 
feet in diameter, favorably situated, produced, in one instance, 
a barrel of sap in twenty-four hours ‘The quantity depends 
also on the number of openings made in the tree. 
The sap from trees growing in the maple orchards, gives an 
average of one pound of sugar to about four gallons of sap; 
varying considerably in different years. One gentleman in 
Bernardston made 300 pounds from 60 trees; another 400 
pounds from 100 trees; a third 500 pounds from 150 trees. 
Some trees will give 10 pounds; some, more. Dr. Rush cites 
an instance of 20 pounds and one ounce having been produced, 
within nine days, in 1789, from a single tree, in Montgomery 
Co., N. Y.; and Michaux quotes the Greensburgh Gazette as 
his authority for saying that 33 pounds have been made in one 
season from a single tree. Mr. Lucius Field, of Leverett, in- 
* Henry W. Cushman, Esq., to whom I am indebted for much valuable infor- 
mation upon this subject. 
+ Dr. Benjamin Rush’s Letter to Thomas Jefferson, on “the Sugar Maple Tree,” 
in the 3d Vol. of the Transactions of the Amer. Philosophical Society, Ist series. 
