( 2 ) 



tritlve juices of the plant outwnrds towards the bark, as in the next 

 figure will be more fully explained. 



Fig. 1, AB C D, reprefents a finall piece of Oak, drawn as nearly 

 as could be done, according to its appearance ^ean tiirough a micro- 

 fcope, prepared by ine for that purpofe, and which piece of wood 

 appears to the naked eye of the fize reprefented at//g-. 2, X. 



The dark fhades at F F, F F, indicates the part where, towards 

 Autumn, the vegetation and increafe for that year ceafe; and about 

 this time, and in this part, the wood becomes exceeding hard, being 

 compofed of fuch fmall venbls, that it is difficult, and at laft im- 

 pofhble to diftinguifli them, for which reafon they alT'ume the ap- 

 pearance of dark flreaks or fliades. Between the letters F F, FF, 

 is contained that fpace, or thicknefs, which the tree acquires 

 through its circumference, in the fpace of one year. 



This fpecies of timber tree, has five different kinds of veflels,. 

 three rifing perpendicularly, and two extending, or fp reading hori- 

 zontally. 



EEE, reprefent the firft fort of thefe perpendicular vefiels,. 

 which are very large, and are produced in the fpring, with the firft 

 rife of the fap. The infides of thefe vefiels are full of a kind of 

 veficles, or little bladders, compofed of very thin membranes, or 

 Ikins, and thefe are to be feen in fig. 3, where, at the letters 

 L K I M, is reprefented a fe(5lion of one of thefe large veflels, di- 

 vided longitudinally, and feen through the microfcope. 



The fecond fort of thefe perpendicular vefleis is much finailer, 

 and is alfo compofed of exceeding fine membranes, intermixed v.itli 

 a kind of Ipots, ^^ hich by the microfcope, appeared to my eye like 

 globules, or little balls, as reprefented in fig. 4, O N, which exhi- 

 bits one of thefe lecond fized vellels, divided longitudinally. 



The third kind of thefe perpendicular vefiels is exceeding fmall, 

 but in great numbers : likewife compofed of cxccflively minute 



