Public Domain Mark
You can use this work for any purpose without restriction under copyright law. Read more about this licence.
Credit
Thesis... on the relative effieciency of certain filters for removing micro-organisms from water, with special reference to the Nordtmeyer-Berkefeld and Pasteur-Chamberland filters / by H. H. Johnston. Public Domain Mark. Source: Wellcome Collection.
Provider
This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.