Measuring Prayer in 19th-Century England

"That July, three months before he set sail [for the United States], the London Contemporary Review published an anonymous letter, 'The Prayer for the Sick: Hints towards a Serious Attempt to Estimate its Value,' along with an introductory note by [John] Tyndall. The letter suggested that, if organized correctly, the efficacy could be tested experimentally through quantitative methods. Tyndall had purposefully picked a fight--what became know[n] as the 'Prayer-Gauge Debate'--the contours of which helped shape the age of scientific naturalism."

From The Age of Scientific Naturalism, edited by Bernard Lightman and Michael S. Reidy