vi TENSION REOUIRED TO RAISE THE SAP i?i 



It may be noticed that the most divergent observations 

 are those made at the higher pressures. 



Comparison of results. When we compare these 

 results with Ewart's, a very wide discrepancy is appar- 

 ent. The results of three of his experiments allow 

 themselves readily to be compared with my figures. 



(1) He found that water travelled in a piece of yew 

 stem, 35 cm. long, at the rate of 11*7 cm. per hour under 

 a head of 3 metres. The head here is nearly 8 - 6 times the 

 length of the transmitting wood. Assuming the velocity 



90 



80 



70 



60 



5 50 



Si 



2 40 



6 



30 



20 



10 



5 6 7 



Units Head 



Fic 20. 



10 



proportional to the pressure, at unit head the water would 

 travel at 1*36 cm. per hour. This rate is stated to be 

 above the average. 



(2) On pp. 51 and 52 of Ewart's paper it is stated that 

 the rate of flow in a piece of yew wood, 25 cm. long, under 

 a head of 3 metres is 26 cm. per hour. In this experiment 

 the head is equal to a column 12 times the length of the 



K 2 



