“Reibungsverlust”

Data:

• “Rechenschieber für Reibungsverlust bei Wasserleitungs-Rohren nach Darcy Fanning von Dr. Jul. Freih. v. Schwarz”.
• E.J. Ponocny, Wien / Ingenieur Rudolf Müller, Wien
• Slide Rule for Friction Loss in Water Pipes.

Question:

1. ???
   Compare the Pickett #12 Slide Rule described in JOS 23(1) (2014) pg.46-50 Andries de Man
   
   Rudolf Müller presented a more complicated device in “Über die Verwendung von Rechenschiebern für die Feststellung der Durchflussverhältnisse bei Rohrleitungen und Canälen”, Österreichische Monatsschrift für den öffentlichen Baudienst 7(2) (February 1901) pg.72-76 but in Plate 10 he shows a ‘regular’ slide rule, that was designed earlier, in 1897, by Dr. Julius Freih. v. Schwarz, produced in approximately 10 copies by Starke & Kämmerer and distributed to friends and acquaintances. Andries de Man
   
   Rudolf Müller (* 1853-06-12 Vienna; † 1926-12-02 Vienna) studied at the Technical University of Vienna. After graduation as a civil engineer in 1876, he worked for the building contractor Baron Schwarz [Karl Freiherr von Schwarz], where he stayed until 1913. See Willi H. Hager, “Hydraulicians in Europe 1800-2000”, Volume 2, pg.797 Andries de Man
   
   Dr. Julius Freiherr von Schwarz (* 1853-06-12; † 1935-11-23) was the son of building contractor Karl Freiherr von Schwarz.
   In 1873 he got his PhD at Tübingen University for a dissertation “Einiges über Falcoiden” Andries de Man
   
   Eduard Ponocny (* 1858-06-19; † 1932-06-14) was a scientific instrument maker in Vienna, trained in the workshop of Starke & Kammerer and started his own workshop in 1897. His oldest son, also called Eduard, took over the business around 1932. See the obituary in Österreichische Zeitschrift für Vermessungswesen, September 1932, p.85 and Planimetrica.
   Note: father and son were referred to as ‘Eduard Ponocny’ or ‘Ed. Ponocny’. But I have not seen ‘E. J. Ponocny’ Between ca. 1899 and 1912 there was also a ‘Mechaniker Josef Ponocny’ in Vienna. Andries de Man