9. When the Complex Facts which nature offers to us are thus decomposed into Simple Facts, the decomposition, in general, leads to the introduction of _Terms_ and Phrases, more or less technical, by which these Simple Facts are described. When Astronomy was thus made a science of measurement, the things measured were soon described as _Hours_, and _Days_, and _Cycles_, _Altitude_ and _Declination_, _Phases_ and _Aspects_. In the same manner, in Music, the concords had names assigned them, as _Diapente_, _Diatessaron_, _Diapason_; in studying Optics, the _Rays_ of light were spoken of as {58} having their course altered by _Reflexion_ and _Refraction_; and when useful observations began to be made in Mechanics, the observers spoke of _Force_, _Pressure_, _Momentum_, _Inertia_, and the like. 10. When we take phenomena in which the leading Idea is Resemblance, and resolve them into precise component Facts, we obtain some kind of Classification; as, for instance, when we lay down certain Rules by which particular trees, or particular animals are to be known. This is the earliest form of Natural History; and the Classification which it involves is that which corresponds, nearly or exactly, with the usual Names of the objects thus classified. 11. Thus the first attempts to render observation certain and exact, lead to a decomposition of the obvious facts into Elementary Facts, connected by the Ideas of Space, Time, Number, Cause, Likeness, and others: and into a Classification of the Simple Facts; a classification more or less just, and marked by Names either common or technical. Elementary Facts, and Individual Objects, thus observed and classified, form the materials of Science; and any improvement in Classification or Nomenclature, or any discovery of a Connexion among the materials thus accumulated, leads us fairly within the precincts of Science. We must now, therefore, consider the manner in which Science is built up of such materials;--the process by which they are brought into their places, and the texture of the bond which unites and cements them. {{59}} CHAPTER IV. OF THE COLLIGATION OF FACTS. APHORISM VII. _Science begins with_ common _observation of facts; but even at this stage, requires that the observations be precise. Hence the sciences which depend upon space and number were the earliest formed. After common observation, come Scientific_ Observation _and_ Experiment. APHORISM VIII. _The Conceptions by which Facts are bound together, are suggested by the sagacity of discoverers. This sagacity cannot be taught. It commonly succeeds by guessing; and this success seems to consist in framing several_ tentative hypotheses _and selecting the right one. But a supply of appropriate hypotheses cannot be constructed by rule, nor without inventive talent._ APHORISM IX.