DARCY'S LAW, FILTRATION, AND PUBLIC HEALTH

Henry Darcy's major publication The Public Fountains of the City of Dijon is his 1856 account of the planning and construction of Dijon's water supply system in 1834-44. The book is famous for Appendix D in which Darcy describes the experiments that led to his law.

Prior to1840, Dijon had a meager water supply consisting of water collected from rooftops and drawn from shallow alluvial wells. As a young engineer, Darcy decided to provide abundant water for Dijon, and accomplished this feat by capturing a spring located 12 km from town, conveying the water through an aqueduct to two reservoirs, through an internal distribution system of one km of cast iron pipes to120 street fountains, all by gravity. The street fountains provided free water for domestic purposes, street cleaning, and fire fighting at intervals of 100 m along the city streets. This improvement in water supply led to better health and increased population in Dijon.

How do the sand experiments relate to the water supply system? They don't. Appendix D of the book is a chapter on filtration, a discussion of various European water supply systems based on surface water, which due to flooding often required filtration. Darcy was highly critical of the London water system because it was expensive and provided poor quality water. Cities that used surface-water had major obstacles in finding enough land to set up filtration galleries. Darcy's goal of perfecting the filtration process led him to propose a filtration tank and more importantly for us two hundred years later, conduct the sand experiments that led to Darcy's Law.

This presentation will include material from Darcy's Public Fountains, a family biography, and photographs of present-day Dijon.