  Pickering has made several important and valid points concerning experiment. Most importantly, he has emphasized that an experimental apparatus is initially rarely capable of producing a valid experimental results and that some adjustment, or tinkering, is required before it does. He has also recognized that both the theory of the apparatus and the theory of the phenomena can enter into the production of a valid experimental result. What one may question, however, is the emphasis he places on these theoretical components. From Millikan onwards, experiments had strongly supported the existence of a fundamental unit of charge and charge quantization. The failure of Morpurgo’s apparatus to produce measurements of integral charge indicated that it was not operating properly and that his theoretical understanding of it was faulty. It was the failure to produce measurements in agreement with what was already known (i.e., the failure of an important experimental check) that caused doubts about Morpurgo’s measurements. This was true regardless of the theoretical models available, or those that Morpurgo was willing to accept. It was only when Morpurgo’s apparatus could reproduce known measurements that it could be trusted and used to search for fractional charge. To be sure, Pickering has allowed a role for the natural world in the production of the experimental result, but it does not seem to be decisive.