cf a Condenser and Air-^mp . 145 



Tig. 7, (PL XrV.) ^tf) a glass vessel with only one aper- 

 ture to be used instead of the upper vessel (a) when the 

 safety valve is considered unnecessary. For the same pur- 

 pose the receiver (^) figs. 1 and 2, may also be used occa- 

 sionally, as all the joints fit each other. (6) a glass stop-cock 

 to be joined occasionally by a pair of collars to the vessel {a) 

 in this figure, or to any other at pleasure. This vessd (a), 

 with its stop-cock being joined to the bottom of the piston (</, 

 fig. 1.), and in the place of the receiver [e) may be exhausted 

 if required. But in order to apply the instrument to the pur- 

 poses of exhaustion, the bottom of the piston should be set in 

 a platform, and have under it a bridge reversed, similar to 

 that represented in fig. 4. — If the instrument were so con- 

 structed, bent tubes with rings of glass and collars might be 

 applied by their fiat joints, and would answer for exhausting 

 jars connected with them. 



Fig. 8, (PL XIV.) tubes differently bended, which may be 

 connected at pleasure by flat joints, so as to form syphons of 

 any size, and conducting pipes in any directioD, and of any 

 length. 



I have to apologize for the minute particularity of this oobh 

 munication ; but as I wish artists to understand me perfccdy, 

 I have preferred to be rather prolix, than obscure. 



I am« dear Sir, with high esteem and respect, 

 your humble servant, 



GILBERT AUSTIN. 



