8. The reader of the _Novum Organon_ may perhaps, in looking at such examples of the Rule, be reminded of some of Bacon's Classes of Instances, as his _instantiæ absentiæ in proximo_, and his _instantiæ migrantes_. But we may remark that Instances classed and treated as Bacon recommends in those parts of his work, could hardly lead to scientific truth. His {226} processes are vitiated by his proposing to himself the _form_ or _cause_ of the property before him, as the object of his inquiry; instead of being content to obtain, in the first place, the _law of phenomena_. Thus his example[46\3] of a Migrating Instance is thus given. "Let the _Nature inquired into_ be that of Whiteness; an Instance Migrating to the production of this property is glass, first whole, and then pulverized; or plain water, and water agitated into a foam; for glass and water are transparent, and not white; but glass powder and foam are white, and not transparent. Hence we must inquire what has happened to the glass or water in that Migration. For it is plain that the _Form of Whiteness_ is conveyed and induced by the crushing of the glass and shaking of the water." No real knowledge has resulted from this line of reasoning:--from taking the Natures and Forms of things and of their qualities for the primary subject of our researches. [Note 46\3: _Nov. Org._ lib. ii. Aph. 28.] 9. We may easily give examples from other subjects in which the Method of Gradation has been used to establish, or to endeavour to establish, very extensive propositions. Thus Laplace's Nebular Hypothesis,--that systems like our solar system are formed by gradual condensation from diffused masses, such as the nebulæ among the stars,--is founded by him upon an application of this Method of Gradation. We see, he conceives, among these nebulæ, instances of all degrees of condensation, from the most loosely diffused fluid, to that separation and solidification of parts by which suns, and satellites, and planets are formed: and thus we have before us instances of systems in all their stages; as in a forest we see trees in every period of growth. How far the examples in this case satisfy the demands of the Method of Gradation, it remains for astronomers and philosophers to examine. Again; this method was used with great success by Macculloch and others to refute the opinion, put in currency by the Wernerian school of geologists, that {227} the rocks called _trap rocks_ must be classed with those to which a _sedimentary_ origin is ascribed. For it was shown that a gradual _transition_ might be traced from those examples in which trap rocks most resembled stratified rocks, to the lavas which have been recently ejected from volcanoes: and that it was impossible to assign a different origin to one portion, and to the other, of this kind of mineral masses; and as the volcanic rocks were certainly not sedimentary, it followed, that the trap rocks were not of that nature.