DISTILLING. 



425 



Eeference has already been made to the Filter, by which foul 

 water can be made pure for human consumption, and we will 

 therefore pass to another mode of obtaining pure water, namely, 

 the Still. 



In former days, if there were a failure of the supply of fresh 

 water on board ship, the whole of the occupants must necessarily 

 perish. Now, however, no such danger exists, as every well- 

 furnished ship carries at least one Still, by means of which the 

 sea-water can be made to abandon its salt, and to give out 

 nothing but pure water fit for drinking. 



Even in cases where no regular Still has been on board, an 

 extemporised Still has been made from a kettle, a gun barrel, 

 or piece of lead piping, or anything of a similar nature. 



The principle of the Still is simple enough, and is shown by 

 the diagram, rather than drawing, on the right hand of the 

 illustration. There is a vessel in which liquid is boiled. 

 From the upper part of it rises a tube through which the 



steam must pass as it is generated. The tube in question is 

 generally of considerable length, and is coiled inside a vessel 

 filled with cold water, rendered colder by ice, if possible. 



As the steam passes through the cold tube condensation 

 takes place, and it becomes liquid again, but deprived of its 

 heavier particles, so that if sea- water be placed in the still, the 

 salt is left in the vessel, and nothing but pure water passes 

 through the tube. In dissecting-rooms a small still is almost 

 invariably kept. Many preparations are of such a nature that 

 the spirit in which they are placed becomes discoloured, and 

 has to be repeatedly changed. Now, even methylated spirit is 



