( 3 ) 



inembranes, and thefe are alfo reprefented wlien cut longitudinally, 

 or lengthways, ^tfg. 4, P Q. 



All thefe perpendicular vefTels, which are found in fo linall a 

 piece of wood as that before reprefented, and which in fize, is about 

 the ninetieth part of a fquare inch, do amount in number, in my 

 opinion, to twenty thoufand ; fo that an Oak tree of four feet in cir- 

 cumference * contains, according to my computation, more than 

 three thoufand two luindred millions of thefe perpendicular veffels, 

 and in a tree of no more than one foot in circumference, will be 

 found two hundred millions of fuch veflels. 



Thefe perpendicular vefiels do, for the moft part, infufe, or inftil 

 their juices into other vefl'els, which are almoft innumerable, lying in 

 an horizontal pofition in the tree, and by the means of which it's bulk 

 or thicknefs is daily increafed : thefe vefTels are of two forts. 



F/g. 2, G G G, reprefents one fort of thefe horizontal vedels, 

 which originally, or at the firft formation of the plant, are derived 

 from the marrow, or pitii, in the centre of it , but afterwards, in 

 great numbers, take tiieir origin from the perpendicular veiTels. 

 Thefe vedels apjieared to my eye like dark flreaks ; but in order to 

 examine them more clearly, I cut a piece of the wood lengthwife, 

 fo that they were cut exa6tly acrofs, and then each of them ap- 

 peared to be formed of five, fix, or even feven veflels joined one 

 on anotlier, as they are reprefented \njig. 4, intermixed among the 

 perpendicular veiTels. 



The other fort of horizontal vefTels, lyijig in great numbers 

 or clufters, clofely joined to each other, though not evenly dif- 

 fufed throughout the wood, when examined in their horizontal 

 pofition, appear as \nfg. 2, AB, or C D, (but when cut tranfverfely, 



* The circumference of a circle being about three times it's diameter, a tree of four feet 

 in circumference, will be fixteen inches indianut;*r, and one of a foot in circumference, four 

 •inches diameter, th; fize reprefented in^^. i. 



