The term ‘Ohm's law’ traditionally denotes the formula of Georg Simon Ohm relating voltage, current, and resistance in metallic conductors. But to students of sensory physiology and its history, ‘Ohm's law’ also denotes another relationship: the fundamental principle of auditory perception that Ohm announced in 1843. This aspect of Ohm's science has attracted very little attention, partly because his galvanic researches so thoroughly eclipsed it in success and importance, and partly because Ohm's work in physiological acoustics had so little immediate impact on the science of his time. On announcing his hypothesis in 1843, Ohm found himself drawn into a bitter dispute with the physicist August Seebeck, who successfully discredited the hypothesis and forced Ohm to withdraw from the field.

As a natural philosopher, Count Rumford is best known for his vehement advocacy of a motion or mechanical hypothesis of heat and for the dramatic experiments that he performed to support this hypothesis. Although a motion hypothesis which held that heat was merely the motion of the ultimate particles of a body had a distinguished history, with advocates that included Bacon, Boyle, Hooke, and Newton, most British natural philosophers by the beginning of the nineteenth century believed that the phenomena associated with heat were caused by an imponderable fluid. William Henry reflected contemporary opinion in 1803, when he wrote:

The former of these opinions [i.e. the existence of caloric], though far from being universally admitted, is now generally received; and the peculiar body, to which the phenomena of heat are referred, has been denominated by M. Lavoisier [as] caloric.

Central to the development of geology has been the growth of systematic empirical observation as a programme of scientific practice. Fieldwork has focused on many objects—strata, fossils, and landforms—and has issued in a variety of products, such as maps, sections, and monographs on regional geology, particular rock formations and fossils. Early in the nineteenth century, above all, many influential geologists sought to define their science as one exclusively of field observation, description, and the accumulation of data. The rise of fieldwork, in Britain as elsewhere, is an important phenomenon in the making of geology. It must be explained.