132 STEPHEN HALES 



His first experiment {Vegetable Staticks, p. lOo), 

 was with a vine, to which he attached a vertical 

 pipe made of three lengths of glass-tubing jointed 

 together. His method is worth notice. He 

 attached the stump to the manometer with a "stiff 

 cement made of melted Beeswax and Turpentine, 

 and bound it over with several folds of wet bladder 

 and pack-thread." We cannot wonder that the 

 making of water-tight connexions was a great 

 difficulty, and we can sympathise with his behef 

 that he could have got a column more than 2 1 feet 

 high but for the leaking of the joints on several 

 occasions. He notes the familiar fact that the 

 vine-stump absorbed water before it began to 

 extrude it. 



He afterwards (pp. 106-7) used a mercury 

 gauge, and registered a root-pressure of 32^ inches 

 or 36 feet $\ inches of water, which he proceeds to 

 compare with his own determination of the blood- 

 pressure of the horse (8 feet) and of other animals. 

 Perhaps the most interesting of his root-pressure 

 experiments was that (p. no) in which several 

 manometers were attached to the branches of a 

 bleeding vine, and showed a result which convinced 

 him that "the force is not from the root only, but 

 must proceed from some power in the stem and 

 branches," a conclusion which some modern 

 workers have also arrived at.;^T • 



Assimilation. 



Hales' belief that plants draw part of their food 

 from the air, and again, that air is the breath of life, 

 of vegetables as well as of animals (p. 148), are 



