This collection pieces together a wealth of material in order to get inside the experience of scientific practice in the long nineteenth century. It aims to reach, or perhaps to facilitate, an understanding of the ways in which the value of scientific knowledge was produced, lived and challenged. The new turn to the history of experience suggests a logic to the compilation of material that is completely original: the sources are not selected according to the historical success of an idea or experiment, but for the ways in which scientific endeavour loaded knowledge claims with political or moral value, coupled with attendant practical justifications. Thus, 'bad ideas' sit alongside 'good'; now discountenanced practices take their place among the revered. In sum, they reveal an experimental culture that was not merely orientated toward cold knowledge or intellectual output, but defined by shifting sets of affective practices and procedures and the making of expertise out of the lived experience of doing science.