(785 ) 
ordinary Barometers lower than at the faid time of Gra"" 
duation. 
And the fpaces anfwering to an inch of Mercury will 
be more or lefs, according to the quantity of Air fo in- 
cluded, and the fmallnefs of the Glafs Cane, in which 
the liquor rifes and falls, and may be augmented almoft 
in any proportion, under that of the fpecifick gravity of 
the Liquor of the Thermometer to Mercury. So as to 
have a foot or more for an inch of Mercury, which is 
another great convenience. 
It has been obferved by fome, that in long keeping 
this Inftrument, the Air included either finds a means to 
efcape, or depofits fome vapours mixt with it, or elfe 
for fome other caufe becomes lefs Elaftick, whereby in 
procefs of time it gives the height of the Mercury fome- 
what greater than it ought 5 but this, if it ftiould hap- 
pen in fome of them, hinders not the ufefblnefs thereof, 
for that it may at any time very e^fily be correfted by 
experiment, and the riljng and falling thereof are the 
things chiefly remarkable in it, the jaft height being 
barely a curicfity. 
In thefe parts of the World, long experience has told 
us, that the rifing of the Mercury forebodes fair weather 
axtcr foul, and an Eafterlyor Northerly wind ^ and that 
the falling thereof, on the contrary fignifies Southerly or 
Wefterly winds, with Rain, or ftormy Winds, or both 5 
which tatter it is of much more conlequence to provide 
againft at Sea than at Land 5 and in a ftorm,the Mercury 
beginning to rife is a fure fign that it begins to abate, as 
has been^Sxperienced in high Latitudes both to the Nor* 
wards and Southwards of the Equator. 
The Form of this Inftrument is (hown in the Cut by 
Fig. 8. wherein 
AB reprefents the Spirit- Thermometer, graduated 
from o, or the freezing point,i through all the pofhble de- 
grees of the heat or cold of the Air^ at kaft in thefe Cli- 
mates. CD 
