t 302 3 



Pig. XIII. A kind of forceps of 

 tongs, to receive the necks of dif- 

 ferent vefTels, 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 

 vefTel 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 instrument is very ufeful for 

 different operations, which, without 

 its help, would require an ailiftant 

 to hold the glafs to keep it from 

 falling. 



INDEX. 



