Bertschinger. Journal für Gas- und Wasserversorgung, 1889, p. 1126.
A record of experiments made at Zürich upon the effect of rate of filtration, scraping, and the influence of vaulting. Rate and vaulting were found to be without effect, but poorer results followed scraping. The numbers of bacteria in the lake-water were too low to allow conclusive results.
—— Journal für Gas- und Wasserversorgung, 1891, p. 684.
A farther account of the Zürich results, with full analyses and a criticism of Fränkel and Piefke’s experiments.
Bolton. Pamphlet, 1884.
Descriptions and statistics of London filters.
Böttcher and Ohnesorge. Zeitschrift für Bauwesen, 1876, p. 343.
A description of the Bremen works, with full plans.
Burton. Water-supply of Towns. London, 1894.
Pages 94-115 are upon filtration and mention a novel method of regulating the rate.