8 § Van-Marum’s Gazometer 
The gazometer is furnifhed with a thermometer f fs 
which i is fo cemented with fealing wax into a piece of. cop- 
per % that the bulb of it.is within the gazometer. By thefe 
means the temperature of the air ufed may be known, and 
its weight accurately afcertained. The tripod on which the 
gazometer ftands facilitates the adjuftment of the apparatus, 
and a brafs bottom fcrewed upon the tripod is furnifhed 
‘with a brafs rim or lip to receive the glafs A and keep it faft 
in its place. Exaétly at the upper level of this rim the, fcale 
aé commences, The {cale is of ivory, and faftened.on a flip 
of brafs, and at the ends are two fquare pieces of brafs, by 
which it is made faft, by means of two ferews, to the, cover 
at the top, and to.the before-mentioned lip. _The-fcale is 
divided i in the common method, by pouring equal meafures 
of water (fuppofe 2 cubic inches) into the glafs, and mark- 
ing the height of each on the feale, or, as the glafles are 
nearly cylindrical except at the neck, it may, be fuficient 
to ufe at once 32 cubic inches, and divide the height,into 
16 equal parts ;, the. neck of the yeflel mutt be divided, as 
above, by 2, cubic inches at a time, 
To explain the ufe of the gazometer it is only sy es nee to 
fhew how the fyphon GF EI is filled at the:;commence- 
ment of the experiment, This is done almoft in the fame 
manner in which M, Lavoifier filled the fyphon, which »he 
employed in order to, fill the lamp ufed in the. experiment 
refpecting the combuftion of oil *.. The method is as fol-: 
lows ;—The two cocks N and P are.to be openedat the fame 
time, and to be kept fo until the cylinder H is completely 
filled with water. The pipe G G, which is open both above 
and below, as the crooked pipe F E is not yet joined: to it at 
F, will be filled at the fame time with the cylinder. The tube. 
G G is then to be fhut below by. the cock 4. This cock is 
fixed into a piece of brafs, which is faftened in the cylindep 
H by four ferews, the heads of which may be {een at 2,4, 2, 7. 
To this piece of metal, made hollow in a perpendicular direc~ 
* See his Chemiftry, Paris edit, 1789, page 495. , 
uon, 
