The empiricism of eighteenth-century experimental science meant that the development of scientific instruments influenced the formulation of new concepts; a two-way process for new theory also affected instrument design. This relationship between concept and instrumentation will be examined by tracing the development of electrical instruments and theory during this period. The different functions fulfilled by these devices will also be discussed. Empiricism was especially important in such a new field of research as electricity, for it gave rise to phenomena that (...) could not have been predicted by theory alone. However, the interpretation of these phenomena, and what the natural philosopher thought he observed, were often unconsciously determined by current ideas and attitudes; the interaction between instrumentally induced phenomena and observation was more complex than was realized at the time. The shortcomings of this empirical approach will be discussed. In the case of electricity this became increasingly apparent during the latter part of the century. The many discoveries had to be placed in a unifying framework before new advances could be made. Instruments, however, continued to play an important role in scientific progress, for they made visible what was hidden in nature. (shrink)