A necessary consequence of these views was that every compound was to be considered as made up of two parts in electrically different states. Thus baryta, consisted of a combination of the electro-positive barium, combined with the electro-negative oxygen; it combined with sulphuric oxide because the preponderating positive electricity it contained met with the negative electricity which prevailed in the sulphuric oxide. Generalising, it may be said that the basic oxides are invariably the positive constituents of salts, whereas the acid oxides are the negative constituents, as proved by the mode in which the two kinds of oxides separated at the poles on electrolysis. Barium sulphate, then, was to be regarded as made up of two entities—BaO and SO3—and hence was to be called sulphate of baryta. Berzelius extended this conception in order to explain the formation of double salts—such, for example, as potash alum, which he regarded as a binary compound of positive potassium sulphate and negative aluminium sulphate, each of which, in its turn, could be resolved into an acidic and a basic oxide of opposite electricities. The dualistic notions of Berzelius led him to the construction of a system of chemical nomenclature and notation which, in its main features, has persisted to this day, and is universally current, with certain modifications, in modern chemical literature. We owe to him the grouping of the elements into metals and metalloids, and also our present system of symbolic notation, whereby even complicated chemical reactions may be expressed in a concise and intelligible manner. Chemical symbols were used by the alchemists; but Berzelius first suggested that a chemical symbol should not only represent the element to which it refers, but also its relative atomic weight. Chemical equations became quantitative as well as qualitative expressions of the facts they denote. Such equations implicitly assumed that, to use Davy’s words, chemistry had passed under the dominion of the mathematical sciences. Professed mathematicians were, however, slow to recognise that the phenomena of chemical action were capable of formal mathematical treatment. Davy relates that on speaking to Laplace of the atomic theory in chemistry, and expressing his belief that the science would ultimately be referred to mathematical laws similar to those he had so profoundly and successfully established with respect to the mechanical properties of matter, the idea was treated in a tone bordering on contempt.