LECT. II. 



HALES'S APPARATUS. 



39 



Fig. 1. 



the action of the juices of plants, as well as in the pheno- 

 mena of the capillary circulation of the blood in animals. 

 In another lecture we shall show that all the parts of living 

 plants and animals soon become impreg- 

 nated with a saline solution into which 

 some part of them is immersed, and that 

 its presence is easily recognised by tests. 

 It will be sufficient for me to refer to the 

 experiments of Hales and the more recent 

 ones of Boucherie. The latter saw a pop- 

 lar 28 metres [nearly 92 feet] in height 

 absorb by its trunk, in 6 days, the enor- 

 mous quantity of 3 hectolitres [about 66 

 imperial gallons] of a solution of pyrolig- 

 nite of iron. 



Hales's Experiments. I shall here no- 

 tice the experiments of Hales, made with 

 the view of measuring what he calls the 

 force of aspiration* of powders and of the 

 stems of trees. 



[This experimenter filled a glass tube, 

 c. r } ij 3 feet long, and J- of an inch dia- 

 meter (Jig. 1.,) with well dried and sifted 

 wood ashes, pressing them close with a 

 rammer. " I tied," he observes, " a piece 

 of linen over the end of the tube at i, to 

 keep the ashes from falling out. I then 

 cemented the tube c fast at r, to the aqueo- 

 mercurial guage, r z; and when I had filled the guage 

 full of water, I immersed it in the cistern of mercury, x; 



* I cannot find the term "force of aspiration " in Hales's Vegetable 

 Statics. The phrases which Hales employs are, " the force with which 

 trees imbibe moisture," and "the imbibing power." J. P. 



Hales's Apparatus for 

 ascertaining the force 

 with which powders 

 imbibe moisture. 



