96 EXPERIMENTS OF HALES. 



as to give rise to two completely opposite in- 

 fluences. 



On the evening of the 30th the water poured 

 into the tube was absorbed; on the 31st it was 

 expelled with a continually increasing force. 



In his experiment XXXVII., HALES fixed, on 

 three branches of a horizontally trained espalier 

 vine, siphon tubes, filled to a certain point with 

 mercury. 



The three branches received their sap from the 

 common stem, that stem from the root. The first 

 branch was 7 feet from the second, the second 22 

 feet 9 inches from the third. The first and third 

 branches were two years old, the middle one was 

 older. 



From the 4th to the 20th of April, the mercury 

 stood, in consequence of the pressure of the sap, 

 higher in the open limb of the tubes than in the 

 other which was attached to the branch. 



The greatest height attained by the mercury was 

 from 21 to 26 inches. 



On the 21st of April, when the flowering was 

 nearly over, the sap in the middle branch went 

 backwards ; it was absorbed, and so considerably, 

 that the mercury stood 4 inches lower in the open 

 limb than in the other. After a rainy night on the 

 24th of April, the sap again rose in the open tube 

 4 inches. 



In the first (lowest) branch, the sap went back 

 on the 29th of April, 9 days after the middle one ; 



