36 HOFFMANN ON THE CIRCULATION 



According to this, there was increase at A from the 9th to 

 the 11th, then from the 12th (through a fall of snow on the 

 11th) decrease; on the 15th increase (through the preceding 

 warmth, and resulting evaporation of moisture from the earth ?) ; 

 at B increase. The sap from the lower orifice was not so dense 

 as that from the upper. 



The reaction of the fresh sap was neutral to blue litmus and 

 turmeric papers on the 8th and 9th of March; on the 15th 

 slightly acid. 



On the 8th and on the 15th the taste was indistinctly sweetish 

 and earthy ; but chemical testing demonstrated the presence of 

 ^r«j9e- sugar, when the fluid was warmed with solution of pot- 

 ash and sulphate of copper, since a red powder was rapidly 

 thrown down. 



14. A birch [Betula puhescens, Ehrh.) 1^ foot in diameter was 

 tapped in various places, in order to discover whether more fluid 

 was effused from the upper or lower part of the stem. This 

 took place on the 14th of March, at three o'clock. 



A, East side, 1^ foot high, gave in 5 minutes 335 drops. 



B, 8 feet .... 120 . . 



A and B were then closed. 



C, North side, 2 feet high, gave in 5 minutes 118 drops. 



D, 8 . . .... 80 . . 



The lower orifice therefore gave more than the upper. 

 The fluids of A and B were neutral with test-papers. 



15. Repetition of the preceding experiment in another birch 

 of the same species and of the same size. Experiment made 

 afler three o'clock on the 14th of March. 



A, N.E. side, 1 foot from the ground, gave in 5 minutes 93 drops. 



B, . . 9 feet .... .... 103 . . 



A and B were closed, and two new holes bored. 



C, North side, 1 foot from the ground, gave in 5 minutes 63 drops. 



D, .. 9 feet .... .... 51 .. 



Here also the lower orifice usually emitted more than the upper. 

 The striking and frequent anomalies which appeared here, as in 

 Experiment 13, will appear abundantly explicable when we 

 reflect what an important influence a very small difference in 

 the condition of the orifices (in regard to depth, diameter, quan- 



