The change is great when in fifty years we pass from the poetical science of Bacon to the mathematical and precise science of Newton.

His own time may well have been struck by the originality and comprehensiveness of such a discriminating arrangement of proofs as the "Prerogative Instances" of the _Novum Organum_, so natural and real, yet never before thus compared and systematized.

But there is a great interval between his method of experimenting, his "_Hunt of Pan_"-- the three tables of Instances, "_Presence_," "_Absence_" and "_Degrees, or Comparisons_," leading to a process of sifting and exclusion, and to the _First Vintage_, or beginnings of theory--and say, for instance, Mill's four methods of experimental inquiry: the method of _agreement_, of _differences_, of _residues_, and of _concomitant variations_.

The course which he marked out so laboriously and so ingeniously for Induction to follow was one which was found to be impracticable, and as barren of results as those deductive philosophies on which he lavished his scorn.

He has left precepts and examples of what he meant by his cross-examining and sifting processes.