34 



HOFFMANN ON THE CIRCULATION 



The specific gravities of the effused fluid exhibited the fol- 

 lowing scale. They were determined in a narrow-neck globular 

 bottle, of about 1 oz. capacity. 



Rain water, 1st filling . . . 25*660 grammes. 



2nd 25-661 



3rd 25-665 



Sap of the Sugar Maple, 



According to this, the specific gravity increases pretty rapidly, 

 and the sweetness of the sap also is readily detected by the 

 tongue. The upper part of the stem contains a less aqueous sap 

 than that near the soil. 



The reaction of the exuded fluid was neutral to blue litmus 

 and to turmeric paper in a fresh condition on the 8th of March ; 

 on the 9th slightly acid, as also on the 15th. 



The amount of sugar contained was tested by adding solution 

 of potash, a few drops of solution of sulphate of copper, and 

 boihng; after a long- continued boiling only was a very small 

 quantity of copper reduced. Some ammonia was set free in 

 this operation. When the mixture was merely allowed to stand 

 at ordinary temperatures, not the least copper was reduced in 

 two hours. It was therefore cane-sugar. 



13. A birch (Betula pubescens, Ehrh.) was tapped in two 

 places at half-past two o'clock on the 8th of March. The base 

 of the trunk was 1 J foot in diameter. 



A, orifice 1 foot from the ground. 



B, ... 7 feet ... 



Both orifices 1 inch deep. Quills were cemented in and the 

 effused fluids caught. On the upper part of this birch a few 

 small branches had been cut off, from which some sap exuded, 

 which, however, did not run down to the bottom. The following 

 quantities flowed out : — 



