PURIFIERS. 



109 



each bend is a siphon, similar to that represented in the annexed woodcut, 

 by which the condensed vapours before mentioned are conveyed to separate 

 vessels, the fluids passing away being of different values (that from the last 

 siphon is the most valuable). 



Fig. 24. 



These pipes must be kept wet in warm and dry weather by small streams 

 of water running on to them from a tank placed at the top of the retort- 

 house. The quick evaporation of this moisture will keep the pipes much 

 colder than if they were completely immersed in water ; because, as a large 



