When common words are appropriated as technical terms, their meaning may be modified, and must be rigorously fixed.

When common words are appropriated as technical terms, their meaning and relations in common use should be retained as far as can conveniently be done.

In framing scientific terms, the appropriation of old words is preferable to the invention of new ones.

In the Ancient Period of Science, Technical Terms were formed in three different ways:-by appropriating common words and fixing their meaning;-by constructing terms containing a description;-by constructing terms containing reference to a theory.

In the 'Induction of Causes' the principal maxim is, that we must be careful to possess, and to apply, with perfect clearness, the Fundamental Idea on which the Induction depends. The Induction of Substance, of Force, of Polarity, go beyond mere laws of phenomena, and may be considered as the Induction cf Causes. The Cause of certain phenomena being inferred, we are led to inquire into the Cause of this Cause, which inquiry must be conducted in the same manner as the previous one; and thus we have the Induction of Ulterior Causes.

'The Law of Continuity' is this:-that a quantity cannot pass from one amount to another by any change of conditions, without passing through all intermediate magnitudes according to the intermediate conditions. It may often be employed to disprove distinctions which have no real foundation. 'The Method of Gradation' consists in taking a number of stages of a property in question, intermediate between two extreme cases which appear to be different. It is employed to determine whether the extreme cases are really distinct or not. 'The Method of Gradation', applied to decide the question, whether the existing phenomena arise from existing causes, leads to this result:-That the phenomena do appear to arise from existing causes, but that the action of existing causes have transgressed their recorded Limits of Intensity. 'The Method of Natural Classification' consists in classing cases, not according to any assumed definition, but according to the connexion of the facts themselves.

The Construction of the Conception very often includes, in a great measure, the Determination of the Magnitudes. The true construction of the conception is frequently suggested by some hypothesis; and in these cases, the hypothesis may be useful, though containing superfluous parts.

The Process of Induction may be resolved into three steps ; the 'Selection of the Idea', the 'Construction of the Conception', and the 'Determination of the Magnitudes'. These three steps correspond to the determination of the 'Independent Variable', the 'formula', and the 'coefficients', in mathematical investigations; or to the 'Argument', the 'Law', and the 'Numerical Data', in a Table of an Inequality. The conceptions involved in scientific truths have attained the requisite degree of clearness by means of the Discussions respecting ideas which have taken place among discoverers and their followers. Such discussions are very far from being unprofitable

'Natural History' ought to form a part of intellectual education, in order to correct certain prejudices which arise from cultivating the intellect by means of mathematics alone and in order to lead the student to see that the division of things into kinds, and the attribution and use of names, are processes susceptible of great precision.

The Methods of Observation of Quantity in general, are 'Numeration', which is precise by the nature of Number; the 'Measurement of Space' and 'of Time', which are easily made precise; the 'Conversion of Space and Time', by which each aids the measurement of the other. The Idea of Space becomes more clear by studying 'Geometry'; the Idea of Force, by studying 'Mechanics'; the Ideas of Likeness, of Kind, of subordination of Classes, by studying 'Natural History'.