( i6S ) 
This Teems to bid fair for an Inflrument, whereby 
the different Levels of Places may be taken } but upon 
a nice Examination, it will be liable to Error. For, 
in the firft Place, tho’ Sand is not alter’d in its Heat or 
Cold fuddenly ^ yet in two or three Hours, as it is 
carried into a warmer or a colder Place, it will become 
hotter or colder, and the lead Degree of Heat or Cold, 
communicated to the Air C B, will alter the Height of 
the Liquor at D, when the Inflrument is made fo fcn- 
lible as I have mention’d. Then if, in carrying the Inffru- 
nient, itfhould be accidentally inclin’d (as in Fig. II.) To 
that the Liquor in the Bottle fhould not cover the Bot- 
tom of the Tube at B, Tome Liquor may fall out of 
the Tube at B, or Tome Air may get into it : each of 
which Accidents, will quite fpoil the Experiment. 
But if this Machine be made portable, without any In- 
conveniency, and be fecur’d againfl the Aclion of Heat 
and Cold (or, which is the fame, if the Alterations by 
Heat and Cold be exadly allow’d for) it will be of ve- 
ry great Ufe and Certainty, in taking the Levels of di~ 
flant Places, provided they be not To far diflant from 
each other, that it requires above fix HoursTimeto car- 
ry the Inflrument from one Place to another ; nay, ve- 
ry diflant Places, even at two or three Days Journey 
from one another, may be taken tolerably well with 
two Inflrument?, nicely adjufled to each other, if they 
be taken notice of by two Obfervers at the fame Hour, 
in fair Weather, and when there is no Wind. 
Now fuch an Inflrument, 1 hope,. I have contriv’d, 
whereby the Difference of Level of two Places, which 
could not be taken in lefs than four or five Days with 
the beft Telefcope Levels, may be taken in as few 
Hours. 
To the Ball C (Fig. IIL) is join’d a recurve Tube B A 
of a very fine Bore, with a fmall Bubble at Top at A, 
whofe 
