Sect. VI. Agriculture and Vegetation. 177 



at the time of reparation, meafured up- 

 wards of -r.ro of an inch. This additional 



\ 



weight is the real meafure of the attraction 

 betwixt that furface of wood and water in, 

 contact. 



THERE is another force that muft con- 

 tribute to raife the fap, viz. the natural at- 

 traction betwixt the conftituent parts of thq 

 fluid. This muft certainly be the cafe, 

 when the fap moves quickly, as in the vine 

 in the bleeding feaibn. Both thefe caufes 

 acting, and the evaporation going on con- 

 tinually from the fuperior parts of the vef- 

 fels, the fap rifes from the roots of the plants 

 to the extremity of their branches. 



t 



BUT nature does not intend that this 

 (hall be done too quickly. There are 

 many fpiral veffels, and many cells into 

 which the fap is depofited, and by which 

 it muft be retarded. In thefe the fap will 

 be much altered in its nature, by the mo- 

 tion of the plants, by the continual mo- 

 N tions 



