The natural sciences in eighteenth-century Britain displayed a devotion to experimental prosecution of what Kuhn referred to as the newly experimental 'Baconian' sciences (electricity, magnetism, heat, chemistry), but also and equally to speculative theorising concerning the causal processes which underlay the often puzzling, even baffling, behaviour of the phenomena revealed by experiment. This paper takes examples from the work of key eighteenth-century figures in order firstly to emphasise the increasing diversity covered by the term 'experiment', and secondly to assess which modalities of experiment might be held to exhibit an echt-Baconian character. It proceeds to examine the speculative dimensions of these examples, insisting upon a comparable diversity, not primarily of theory-content, though that is of course present, but of epistemic dispositions with respect to theoretical speculation itself. Recognising these diverse modalities in our key terms is a necessary prerequisite, it is held by way of conclusion, to historical understanding of the kinds of work exhibited in our exemplars, and of the meanings such integrative work had for its practitioners.