(651) 
pieces of Deal board ( Poplar would have been better ) each 
about two foot long,and a foot or more in breadth, ( A.B), 
Thefe I got well plained , and iliotren , that their edges /^g^' /' 
might meet even together* Of thefe two, fet edge by edge, 
I faftened each end between two ledges of Oak (CC^of two inch- 
es broad and long enough to reach athwart both boards, (but one 
ledge, if it be thick enough , might be mgck to ferve each end , by 
making hollow furrows or gutters in it to receive the ends ef the 
boardsjand fo I fixed both boards in,as pannels are fet in V/ainfcor, 
This done,fappofing-^of an inch to be the utniofl didance that 
thefe two boards wouid fhrink afunder in dried weather (for it- 
mattered not much, though it fliould be fomewhat more or lefs)I 
took a thi n piece of Brafs(D.Jof two or three inches long and inch 
broad , and upon one edge towards the end I meafur'd ^ofan inchs 
(which was the utmoft diftance I fuppofed the two boards v/ould 
gape afTunder;) which fpace (d.d.) I divided intofiveequal parts, 
and with a fmall file made them into fo many fine teeth, like t hofe 
of a warch- wheel. This piece of Brafs 1 plac'd fiat , acrofs the 
luncture of the two boards,nayling ir5 one end, by means of tw o 
Tmall holes (b.b, ) to the board A. only, and leaving the other end, 
which is the toothed one, free,aod reaching to a compeieot di fiance 
over the board(B.) to which it had no coherence. Next I made a 
pinion, (confiftingof as many teeth as the Brafs had) (e)upon the 
end of a piece of thick Ironw^ire; This Axel(F^wiih its pinion 
(ej Ifo fadaed to the other bo3rd(B) by means of the Brachiolum 
(E,)and fo adapted to the teeth of the Brafs plate, ihat when the 
boards do flirinkafumder, the Brafs being drawn a little away, 
muft needs turn this Axel Cby means of its toothed pinion) more or 
lefs; and fo ifever it happen% that the boards gape but a quarrerof 
aainch ailundcr, this Axel will have made one intire revolution o 
Wherefore I put a long index (G.GJ upon the extremity of this 
Axel, and madea circle round it with the ufual graduations , num- 
bered from what point I pleafed,and the motion of the index back 
or forward J flie^vs me the degrees of the drought or moifture of the 
Ayr. Kowihis. Axel may be made to cooie through a round 
plate of wood or Mettle that hidesthe contrivance all but the hand 
and figures, as in a clock or Watch. Tis to be noted more ovcr^ 
thar the boards mufl be faflned to the ledges, only at the outer edg- 
es, as at a.a.a.a. that they may have the more liberty of fw^ellingand 
flirinkingafTunder.The commodioufnefsof this kind of Hjgrofco fe'in 
comparifon of thofe made of wild Oat-hcards m.iy befi be cbfc-r- 
