APPENDIX. 339 
I 
it is joined to the Tube, that no Air pafschat 
way. 
15. The bigger the globofe Body is, the 
more weighty it ought to be, thereby the 
more eft'edually to keep it in a low depend- 
ing Pofture ; elfe the Buoyancy of its con- 
tained Air might raife it as high or higher 
than the upper part of the Machine, whereby 
Water riifliing in to the Top of the Tube 
no Obfervation could be made, the Rod be- 
ing thereby moiftened from End to End. 
When one Experiment has been made, the 
Rod and Tube muft be wiped very clean, be- 
fore another be repeated. 
14. This Sea- Gage being thus prepared, a 
large Buoy muft be fixed to it, which ought 
to be a large piece of folid Fir, or any 
other light folid Wood, Well covered with 
Tar, to prevent any Waters being prefled 
into the Sap-Veffels ; for I have found by 
Experience chat Wood which was confider- 
ably lighter chan Water, has by being greatly 
comprefled in Water, become immediately- 
fpecifically heavier than Water, for the con- 
ftituent Parts of all Vegetables are fpecifically 
heavier than Water. If the Buoy be made 
of a Bladder or hollow Globe, with its Ori- 
Z 2 fice 
