WRITERS upon science have gone on up to modern times forming such technical terms as they had occasion for, by the three processes above {270} described;--namely, appropriating and limiting words in common use;--constructing for themselves words descriptive of the conception which they wished to convey;--or framing terms which by their signification imply the adoption of a theory. Thus among the terms introduced by the study of the connexion between magnetism and electricity, the word _pole_ is an example of the first kind; the name of the subject, _electro-magnetism_, of the second; and the term _current_, involving an hypothesis of the motion of a fluid, is an instance of the third class. In chemistry, the term _salt_ was adopted from common language, and its meaning extended to denote any compound of a certain kind; the term _neutral_ salt implied the notion of a balanced opposition in the two elements of the compound; and such words as _subacid_ and _superacid_, invented on purpose, were introduced to indicate the cases in which this balance was not attained. Again, when the phlogistic theory of chemistry was established, the term _phlogiston_ was introduced to express the theory, and from this such terms as _phlogisticated_ and _dephlogisticated_ were derived, exclusively words of science. But in such instances as have just been given, we approach towards a systematic modification of terms, which is a peculiar process of modern times. Of this, modern chemistry forms a prominent example, which we shall soon consider, but we shall first notice the other processes mentioned in the Aphorism.