Separating substances from liquids a hundred years ago was still a novel chore and not even as easy as a car insurance comparison is today.

 

Air and Gases in Water.-A considerable amount of air generally exists in water, and is taken up by the gills of fishes, assisting them to accomplish the proper aeration, or rather oxygenation, of their blood. The air usually mingled with water may be expelled by boiling, but is absorbed again if the boiled water is agitated with access of the atmos­phere.

 

Now, that particular segment doesn’t make a great deal of sense in the grand sense of things, but it would appear that the author is trying to talk about the purification or the impurities that can be found or removed from water.