lo ; 



cut or fawn acrofs, we obferve tlie circles, denoting cacli 3^ear's 

 growth to approach very near together, we may eafiiy conclude 

 that fuch timber is firm and durable, efpecially if we -perceive 

 great part of thefe circles to be moiftened or tinged with a refinous 

 or gummy fubftance, named Turpentine. 



The produ6Vion or growth of the Fir is fhewn in Plate ^-fg- 7. 

 which reprcfents a fmall piece of this wood, as feen by the micro- 

 fcope, when cut tranfverfely, in order to fliew the difference be- 

 tween the perpendicular veilels formed in the Spring, and tliofe pro- 

 duced in Autumn, when the growth ceafes. 



The natural fize of the fpace contained between ABC, or EFG, 

 is about the fifteenth part of an inch in length ; ABFG, denote that 

 portion of the wood formed towards the latter end of the year, and 

 the line of feparation appearing at B F, is the place where the increafe 

 for that year ceafed. BCEF indicate a part of the fame wood, 

 produced in the beginning of the following year. 



DD, and GG, are the horizontal velT'els, which in tliis wood are 

 placed very clofe to each other, fo that when cut tranfverfely it is 

 difficult to diftinguifli them. 



In this figure, we fee.the difference between the velTels formed at 

 the beginniiig and at the end of each year's growth. And if the wood 

 here reprefented, within the fpace ABC (which is the fifteenth part 

 of an inch) required two years to enlarge the femidiameter of the 

 tree to that thicknels, it follows, that in this fpace there will be two 

 rows or circles of the compact vellels pi6tured, between AB. More- 

 over, the piece of wood wliich is here defcribed was from a tree of 

 quick growth, and timber of flower growth not only would produce 

 fewer of the large veficls, but alfo thofe vefibls firlt formed in the 

 fpring would be fmaller in proportioii, efpecially if growing in a 

 colder country, and in a good foil. In a word, the nearer the cir- 

 cles before mentioned approach togetlier, tlie flower was the 

 growth, and tins fpecies of Fir is the moft durable. 



