EXPERIMENTS OF HALES. 95 



may be proper here to develop more clearly the 

 grounds of the opinion, that the cause of the efflux 

 of the sap of the vine is a transient one. Perhaps 

 some one may thus be induced to decide experi- 

 mentally all the questions connected with this 

 remarkable phenomenon. 



HALES, in his experiment XXXIV., cut off a 

 vine-stem 7 feet above the ground, and attached to HALES! 

 the trunk tubes of 7 feet long, joined together. 

 Below the cut there were no branches. This was 

 done on the 30th of March, at 3 P.M. 



As the stem poured out no sap on that day, he 

 poured water into the attached tube to the height 

 of two feet. 



This water was absorbed by the stem, so that 

 about 8 P.M., the water had fallen to 3 inches in 

 the tube. 



The next day, 1 past 6 A.M., the sap stood 3 Ri *e of the 



sap in a 



inches higher than at 8 the evening before. From vine, 

 this time the sap continued to rise, till it reached a 

 height of 21 feet. It would perhaps, says HALES, 

 have risen higher, had the joinings of the tubes been 

 more water-tight. 



Whatever opinion we may entertain as to the This rise 

 cause of the efflux and pressure of the sap, it is 

 impossible to suppose that the mechanical or any 

 other structure or quality of the radical fibres, the 

 spongioles, or the inner parts of the vine-stem 

 generally, can have changed so much between the 

 evening of the 30th and the morning of the 31st, 



