METHODS OF THE EARTH-SCIENCES 479 



seen. Only a part of the elements and aspects of complex phenomena 

 present themselves at once to even the best observational minds. 

 Some parts of the complex are necessarily obscure. Some of the most 

 significant elements are liable to be unimpressive. These unobtrusive 

 but yet vital elements will certainly escape observation unless the 

 mind is forced to seek them out, and to seek them out diligently, 

 acutely, and intensely. To make a reasonably complete set of obser- 

 vations, the mind must not only see what spontaneously arrests its 

 attention, but it must immediately draw out from what it observes 

 inferences, interpretations, and hypotheses to promote further obser- 

 vations. It must at once be seen that if a given inference be correct, 

 certain collateral phenomena must accompany it. If another inference 

 be correct, certain other phenomena must accompany it. If still a 

 third interpretation be the true one, yet other phenomena must be 

 present to give proof of it. Once these suggestions have arisen, the 

 observer seeks out the phenomena that discriminate between them, 

 and, under such stimulus, phenomena that would otherwise have 

 wholly escaped attention at once come into view because the eye has 

 now been focused for them. It may be affirmed with great confi- 

 dence that without the active and instantaneous use of these con- 

 current processes the observer will rarely, if ever, record the whole 

 of any one set of significant elements, much less the whole of all sets. 

 His record will contain incomplete parts of different sets of significant 

 elements, but no complete set of any one. The obscure factors of each 

 set are quite sure to be overlooked and the obtrusive factors of 

 several sets indiscriminately commingled. The method of colorless 

 observation is thus seriously defective in the completeness of its pro- 

 ducts, while it successfully guards them from bias. 



Standing over against it, in strong contrast, is the method which 

 at once endeavors to seek out and put together the phenomena that 

 are thought to be significant. This leads promptly to the construction 

 of a theory or an explanation which soon comes to guide the work and 

 gives rise to 



The Method of the Ruling Theory 



The chief effort here centres on an elucidation of phenomena, not 

 on an exhaustive determination of the facts. Properly enough the 

 crown of the work in the end, explanation is brought to the forefront 

 and eagerly made the immediate object of endeavor. As soon as a 

 phenomenon is presented, a theory of elucidation is framed. Laudable 

 enough in itself, the theory is liable to be framed before the phenom- 

 ena are fully and accurately observed. The elucidation is likely to 

 embrace only the more obtrusive phenomena, not the full complement 

 of the obtrusive and the unimpressive. The field is quite likely to 

 present many repetitions of the leading phenomena and a theory 



