C 324 ] 
do thereby caufe the overflowing ebullition of the 
water. On which account it is probable, that lefs 
fpirit of fait is formed and raifed by ventilation than 
without it. As alfo on account of the frefli air 
afeending, not from the bottom of tlie flill, where 
is the greatefl: plenty of fait, efpecially towards the 
latter end of each diflillation j but about three inches 
from the bottom, viz. principally from tlie many 
holes at the furface of the air-box. 
2 5. And whereas the quantity raifed from the 
flill, and diftilled into the calk-receiver, cannot be 
feen ; the proper quantity to be diHilled in each 
diflillation may with great accuracy be known, by 
having a well-clofed pewter bottle, of the fize of 
about half a pint, with a brafs wire as big as a goofe 
quill, fixed to it, the wire to pafs through the re- 
ceiver-cafk, near the bung- hole, which the floating 
pewter bottle will raife up, till the marks on the 
wire appear juft above the calk. I made ufe of a 
glals phial for this purpofe. This wire will rife and 
fall freely, notwithflanding the motion of the fliip, 
if it palTes not only through the wood of the calk, 
but alfo through a metalline pipe two or three inches 
long, fixed in that hole. And it will be known by 
the limmering or boiling noife of the water in the 
flill, whether it is hot enough to diflil ; for the 
running of the water into the receiver-calk cannot 
be feen. 
26. As it might be fufpeded', that more fpirit of. 
fait would be raifed, and diftilled over in the venti- 
lating way, than without it-, having procured 1 8 
gallons of fea- water by the Margate hoy, which was 
taken up at fome diftance from the lliore, I put three 
gallons 
