INVESTIGATION ENCOURAGED 



menting with varieties of sand dropped about an upright 

 darning-needle established the principles governing the 

 angle of rest for falling detritus. 



" His ability to retain in his mind various phases of 

 geological evidence, and develop them as time progressed, 

 was likewise remarkable. Thus, in 1889, in his teaching 

 he laid much more stress on the influence of the Cincin- 

 nati uplift in determining the character of the rocks of the 

 interior of the continent than he had previously done in 

 his Manual, for he said he had never so fully realized its 

 importance as he had that year. 



" Nor were his students compelled to receive obsolete 

 theories or time-worn illustrations because he had held or 

 used them in the past. On the contrary, they were kept 

 informed of the newest discoveries and latest phases of 

 geological thought and urged to judge for themselves of 

 their importance and bearing upon previously attested 

 principles. With all the varied lines of thought and dis- 

 covery he kept in closest touch, and seemed equally ap- 

 preciative of their value, whether they related to the 

 eruptions of Kilauea, the Algonquin formation, mesozoic 

 mammals, the causes of oscillation of the earth's surface, 

 or what not. Of this progressiveness and appreciation of 

 all additions to the sum of geological knowledge his newly 

 published Manual gives sufficient evidence. 



" The quality in an investigator which, other things 

 being equal, he seemed to esteem most highly, was that 

 of carefulness. How often were his students advised to 

 trust or to doubt the statements of an author according 

 as he was or was not, in the opinion of Professor Dana, a 

 careful man ! With hasty and ill-considered conclusions 

 or elaborate theories built from meagre observations he 

 had no patience, but to opinions which he believed had 

 been derived from a careful and thorough study of facts 

 he was ever ready to give the fullest consideration, how- 

 ever much they might be opposed to his previous con- 

 clusions. ' More,' he said, ' could be learned by studying 

 unconformities than conformities,' and this he believed 

 to be as true of unconformable opinions as of heterogene- 

 ous strata. 



The awakening in his mind of the interest in science 

 which became the ruling passion of his life, and led to his 

 signal achievements for its advance, Professor Dana used 



175 



