■266 Of the JVcod of Trees. 
.flick, and then the flick being drawn out, will leave the 
ribband in the form of a tube u and of one of thefe air 
veffels, for that which upon the unwreathing of the veffel 
fieems to be a plate, is as it were a natural ribband, con- 
lifting of a certain number of threads or round fibres, 
Handing parallel as the threads do in a ribband ; and as 
in a ribband fo here, the fibres which make the warp and 
run fpirally, do not grow together, but are held in that 
pofition by other tranfverfe fibres which embrace them, 
and are in the place of the woof. 
And as the faid fibres are tranfverfly continued, thereby 
making a warp and woof, fo are they ( as in divers 
woollen manufactures) of different bulk; thofe of the 
former being ftronger and bigger than thofe of the latter; 
by which means, as cloth and filk will ufually tear fooner 
one way than another; fo here while the warp, or thofe 
fibres which run fpirally are unwreathed, without break¬ 
ing the fmaller ones which hold them together, eafily 
tear all the way. 
In the following figures are Ihewn the pofition of the 
veffels in feveral forts of timber cut length-wife and crofs- 
wife as follows : 
Fig. 507. reprefents a fmall piece of the wood of an 
oak-tree, cut tranfverfly, and of its natural fize; and fig. 
508. A B C D, fhews the fame piece as it appeared be¬ 
fore the microfcope when greatly magnified, whereof the 
parts F F feemed to be brown dark ftreaks, the wood in¬ 
cluded between the fpaces H I and K L, is the breadth 
of that circle which the tree had increafed in one year. 
E E are the cavities of very large air veffels, which run 
the lengthway of the tree. Thefe large veffels are com- 
pofed of feveral fmaller membranes, as may be feen at 
fi cr. 
® Grew Ana. of Plant, p. 117. 
