This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
It consists of a covered iron cylinder, with a large manhole in the side near the bottom for removing the spent charcoal. The float regulates the stream of liquid to be filtered automatically from the cistern.
Fig 17. - The Wagner Charcoal Filter.