"In a letter to Ampère dated 3 September 1822, Faraday lamented, "I am unfortunate in a want of mathematical knowledge and the power of entering with facility into abstract reasoning, I am obliged to feel my way by facts closely placed together." ... Faraday's "facts" were his experiments, both published and unpublished. During a period of 23 years, 1831–54, he compiled the results of those experiments into three volumes, called Experimental Researches in Electricity ... A most remarkable thing is that there was not a single formula in this monumental compilation, which showed that Faraday was feeling his way, guided only by geometric intuition without any precise algebraic formulation."