[ 302 J 
Fig. XIN. A kind of forceps or 
tongs, to receive the necks of dif- 
ferent veffels, in which air is to 
be extricated by heat. It is fixed 
by the fcrew to the brim of the 
water-trough, or to’ the box of 
mercury; and the neck of the glafs 
vefiel is fqueezed between the two 
branches by means of the moveable 
ring, by which ‘they may be more 
‘or lefs fqueezed together, according 
to the fize of the neck of the glafs. 
‘This inftrument is very ufeful for — 
different operations, which, without 
its help, would require an affiftant 
to hold the glafs to keep it from 
falling. 
“INDEX 
