  He uses Morpurgo’s search for free quarks, or fractional charges of \(\tfrac{1}{3} e\) or \(\tfrac{2}{3} e\), where \(e\) is the charge of the electron. (See also (Gooding 1992)). Morpurgo used a modern Millikan-type apparatus and initially found a continuous distribution of charge values. Following some tinkering with the apparatus, Morpurgo found that if he separated the capacitor plates he obtained only integral values of charge. “After some theoretical analysis, Morpurgo concluded that he now had his apparatus working properly, and reported his failure to find any evidence for fractional charges” (Pickering 1987, p. 197). 