SIR CHARLES LTELL. 515 



really derived deductively, tliough only after the broader principles 

 have been independently established by induction. But this can be 

 safely done only after the lowest or merely descriptive generalizations 

 have presented the problems and the tests, between which and the 

 highest generalizations explanatory connections are sought by the 

 deductions and verifications of jihysical science. 



A far more intimate actual acquaintance than Bacon even dreamt of 

 with tiie principles of physical causation had been attained in dynamical 

 science, and was familiar to many students of geology during the 

 eighteenth century ; principles which are almost as remote from the 

 science of Bacon's time as from that of Aristotle's. These principles, 

 and the examples of their application to the explanation of natural 

 phenomena, gave a direction to the inquiries of geologists which was 

 naturally enough looked upon as rash in speculation, and even irrev- 

 erent in spirit, by all who did not share in the insight of these thinkers. 

 The possibility of explaiuhig the phenomena of the earth's formations 

 by means of the causes in actual and normal operations, and not any 

 disrespect for miraculous causes, but a preference for the explanations 

 which to their trained imaginations appeared possible, " without vio- 

 lence, without fictions, without hypotheses, without miracles," deter- 

 mined the theories of the uniformitarians, and especially those of 

 Hutton and his school. The very conception of geology as a branch 

 of physical science, and as allied with Newtonian astronomy, physical 

 geography, and meteorology, divided it sharply from the cosmological 

 speculations which, without foundation in inductions, had previously 

 served as principles of exj^lanation in this science. Hutton was the 

 first to declare that geology is in no wise concerned with questions as 

 to the origin of things. But the very name ''origin" had to be con- 

 verted from its familiar absolute meaning, as a synonyme of miraculous 

 creation, to its meaning in modern science, that of natural production. 

 The revolution about to take place in geology was first clearly apparent 

 to those thinkers who were familiar with and trained in the applications 

 of dynamical principles to the explanation of natural phenomena, not 

 onl}'^ in the regularities and recurrences of these jjhenomena, but also 

 in the gradual changes, and the progressions in their conditions, which 

 these principles implied. Playfiir's illustrations of Hutton's theories 

 were studies undertaken in the spirit of this philosophy. But as yet 

 the lower and merely descriptive facts of the science were far too few 

 and incomplete to afford definite problems or decisive tests of theory. 

 Playfair's work was published in 1797, the year in which Lyell was 

 born. Ten years later, in 1807, the Geological Society of London 



