62 



cate it to, and promote it in, other bodies. 

 Accordingly, we observe the sap of the tree 

 first breaking out like sweat upon the sur- 

 face of the bark, soon corroding the outer 

 bark, next communicating the disease to 

 the periRgneum and the wood.^ 



Sometimes contractions, indurations, and 

 rotting of the bark, are. produced without 

 this ragged appearance, which are equally 

 dangerous, as they are effects of the same 

 cause. 



And it will be found that the disposi- 

 tion of the trees to canker, is, ceteris paribus, 

 in proportion to the transverse strength or 

 power of the bark, i. e. the aggregate power 

 of the transverse baric, and the transverse 

 cohesion of the longitudinal, taken toge- 

 ther. So the disposition to canker will be, 



