Science and technology were far more closely related between 1870 and 1900 than in any earlier period. In the last three decades of the nineteenth century there were few branches of industry that were not affected by new scientific discoveries, although this is by no means the same as saying that traditional empirical methods were entirely or even largely ousted. Empiricism remained dominant in many industries; in some it remains so to the present day; but after 1870 we can clearly see the beginnings of the scientific industry of the twentieth century. The changed outlook is naturally more apparent in the new industries—such as the electrical industry—that originated wholly in scientific discovery than in those, already long established, in which the application of science resulted to a great extent in improving old processes rather than in creating quite new ones.

While the close relationship between science and technology within this period is evident, it is in many instances exceedingly difficult to distinguish cause from effect. Sometimes a purely scientific discovery, resulting from research with no practical objective in mind, was of such obvious practical importance that its commercial development followed almost as a matter of course. The development of the dyestuffs industry was a conspicuous example: the first coal-tar dye was the result of an unsuccessful—and, as we now know, wholly misguided—attempt to synthesise quinine. Other scientific discoveries, however, became significant primarily because contemporary conditions favoured their application; in different circumstances their historical significance might have been slight, or have been apparent at a much later date.