INVESTIGATIONS NEEDED. 191 



may be well to remember that we are everywhere surrounded 

 by objects for scientific research demanding our utmost talent, 

 patience and skill, but sure to give ample and profitable 

 results to every diligent inquirer. We are often inclined to 

 encourage ourselves to remain in ignorance and idleness by 

 dreaming of grand opportunities for study in some far-off 

 time or place, but let us all keep in mind the fact, so familiar 

 to every thoughtful student of nature, that within the limited 

 circle of our vision lie concealed more mysteries than with 

 our best endeavors we can ever solve. 



Observations on the Phessure of Sap. 



The following tab'; s show the maximum and minimum 

 pressures, with the time when each occurred, as indicated by 

 the several mercurial gauges attached to the species named. 

 The pressure is given in inches of mercury, which may be 

 changed to feet of water by multiplying the number of inches 

 of mercury by 13.6 (its specific gravity), and dividing the 

 product by 12, to reduce inches of water to feet. 



The black birch is Betula lenta; the sugar maple, Acer 

 saccharinum; and the vine, Vitis cestivalis. 



The birch was a fine, sound forest-tree, six and one-half 

 feet in circumference, and seventy feet in height. The maple 

 was a heulthy shade-tree, sixty feet in height, and five feet in 

 circumference. The vine was a vigorous wild summer-grape, 

 and the gauge was applied to a branch near the ground. The 

 maiu stem was fo r inches in circumference, and the branch 

 about two and one-half inches. 



The birch-roots were entirely detached from the tree, and 

 were about three inches in circumference at the large end, 

 where the ijausfes were attached. The root No. 2 was not 

 tested until No. 1 was injured, and the greatest pressure for 

 the season was past. 



In the table for the black birch, the first or upper figures 

 for each day are the observations on the upper gauge, and 

 the next line gives those of the lower gauge. The distance 

 between the gauges was first 30.20 feet, and afterward 42.20 

 feet, the upper gauge haviug been raised 12 feet April 

 25th. 



