5 26 THE POPULAR SCIENCE MONTHLY. 



mineral specimens which particularize, as observed, characters that do 

 not appear on the specimens given them to determine, although they 

 may be the correct characters of some other mineral. There is usually 

 no want of honesty in this, but, deceived by some accident, the student 

 has made a Avrong guess, and then imagined that he saw on the speci- 

 men those characters which he knew from the descriptions ought to 

 appear on the assumed mineral. So, also, it not unfrequently hapjjens 

 that a student in qualitative analysis, who has obtained some hints in 

 regard to the composition of his solution, will torture his observations 

 until they seem to him to confirm his erroneous inferences ; and again 

 the student in quantitative analysis, who finds out the exact weight 

 he ought to obtain, is often insensibly influenced by this knowledge 

 in the washing and ignition of his precipitate, or in some other way 

 and thus obtains results whose only apparent fault may be a too close 

 agreement with theory, but which, nevertheless, are not accurate be- 

 cause not true. It is evident how fatal such faults as these must be 

 to the investigation of truth, and they are equally destructive of all 

 scientific scholarship. Their effect on the student is so marked that 

 although he may deceive himself, he will rarely deceive his teacher. 

 That he should lose confidence in his own results is, to the teacher, 

 one of the most marked indications of such false methods of study, but 

 the student usually refers his want of success to any cause but the real 

 one his own untruthfulness. He will complain of the teacher, or of 

 the methods of instruction, and may even persuade himself that all 

 scientific results are as imcertain as his own. As I have said, mere 

 ordinary truthfulness, which spurns any conscious deception, will not 

 save us from falling into such faults. Our scientific study demands a 

 much hiorher order of truthfulness than this. "We should so love the 

 truth above all price as to strive for it with single-hearted and un- 

 swerving pvtrpose. We must be constantly on our guard to avoid any 

 circumstance which would tend to bias our minds or warp our judg- 

 ments, and we must make the attainment of the truth our sole motive 

 guide and end. 



It remains for me, befoi-e closing this address, to say a few words 

 on what I have called the subjective aspect of scientific study. Sci- 

 ence offers us not only a mass of phenomena to be observed, but also 

 a body of truths which have been deduced from these observations ; 

 and, without the power of drawing correct inferences from the data 

 acquired, exact observations would be of little value. I have already 

 described the inductive method of reasoning, and illustrated it by two 

 noteworthy examples, and, in a humbler measure, we must apply the 

 same method in our daily work in the laboratory. "We must learn 

 how to vary our exjjeriments so as to eliminate the accidental circum- 

 stances, and make evident the essential conditions of the phenomena 

 we are studying. Such power can only be acquired by practice, and 

 a somewhat long experience in active teaching has convinced me that 



