of equal intelligence, training, and experience in their conclusions will generally differ from one another by a constant or nearly constant quantity, and each will differ from the truth. This difference from the truth in each individual is his personal equation or habitual error. Many investigators now correct their results for this constant error, but nowhere in the realm of knowledge are the processes for making this correction so perfectly worked out as in the physical sciences, geodesy and astronomy. A party of astronomers was once about to be sent on service to the southern hemisphere. Their personal equations were carefully ascertained, when it occurred to one of them that in the hemisphere to which they were going the apparent celestial movements would be reversed, and that their errors ought to be reinvestigated for stars of apparent reverse motion. This was done, when the differences were found to be oppositely as large as before. There was, however, one individual in the party to whom it mattered not which way the stars moved, for he had no personal equation in either case.
It is the duty of the scientist to sift facts from theory, and he who is thus engaged constantly in separating what is really known from belief or mere theory gains intellectual strength and an appreciation for true honesty. The ability to weigh evidence and distinguish between it and the flights of the imagination is the natural foundation of greatness in all scientific work; and in proportion to his ability to rise into this lofty realm is a man's opinion and work entitled to authority.
The natural and physical sciences demand our attention on account of their technical applications in the arts, and the admirable preparation which they give for all practical work when concrete things are the objective study. The colleges that teach pure mathematics, languages, history, and philosophy, without their application to the affairs of mankind, do not get beyond the threshold of education. They merely place in their students' hands tools for work without training them in their uses, or to appreciate the variety and beauty of their finished product. It is certainly a high and responsible calling to instruct young men from text-books in what has long been accepted as truth, but the higher functions of a true education rise into the sphere of application and original investigation; and I believe the few institutions that strive to this end are doing more for the real intellectual advancement of mankind than all the traditional schools on record. Without the application of the instruments of knowledge, the pretense and self-stultification born in the class room often result in the dangerous and pernicious idea that it is better to be brilliant than to be sound, better to rely on opinion and faith than on experiment and knowledge. Too
