October 2, 1008] 



SCIENCE 



447 



■wliieli a driver pushes vertically downwards on a 

 moving cart is an inactive force, tlie vertical pull 

 of the earth on a railway train which moves 

 along a level track is an inactive force. 



An active force is said to do work and the 

 amount of work done in a given time is equal to 

 the product of the force and the distance that the 

 body has moved in the direction of the force. 



This is taken almost verbatim from the 

 text-book on " Elementary Mechanics " which 

 was recently used with a freshman class in 

 " one of our best technical schools (only 126 

 pages of the text were covered during the 

 excessively short time allotted to this subject) 

 and J/S per cent, of the class at the time of 

 the final examination (counting the SO per 

 cent, who were so hopelessly deficient that they 

 were not allowed even to try the final examina- 

 tion) were so deficient in physical imagina- 

 tion, or power of perception, or whatever one 

 may prefer to call it, that they blindly cal- 

 culated that the man was doing nearly twice 

 as much work as the mule in the following 

 problem: 



A cart moves northwards with a velocity of 

 6 feet per second, a mule pulls northwards on the 

 cart with a force of 90 pounds, and a man exerts 

 on the cart a downward force of 150 pounds. At 

 what rate is work done by the mule and at what 

 rate is work done by the man? 



To have named the part of his body the man 

 used in pushing down on the cart might have 

 stimulated the perceptive powers of the dullest 

 members of the class; indeed the instruction 

 during the term did resolve itself many times 

 into things as unreservedly elemental as this ; 

 hut have we not a right to expect our students, 

 at least at examination time when their 

 greatest effort is put forth, to be able to 

 handle abstract ( !) problems like this of the 

 hard-working cart driver and his pampered 

 mule? 



SCIENTIFIC PERCEPTION 



I was greatly pleased to see Professor Swain 

 bring up Sir William Hamilton's ideas, 

 seventy years old. Perhaps your readers will 

 welcome an idea from William Whewell which 

 is also seventy years old. It is almost the only 

 idea I was able to find years ago when I read 

 the " Philosophy of the Inductive Sciences," 



but it is a creditable thing to have produced 

 one idea; indeed, it would be a creditable 

 thing in our time even to adopt ideas ! 

 Whewell says that ideas of perfect precision 

 are a paramount possession (the four p's are 

 Whewell's ; he might well have omitted at least 

 one of them as I do in the paraphrase). Noth- 

 ing is so essential in the acquirement of real 

 knowledge of physical things as the possession 

 of precise ideas, not indeed because a perfect 

 precision is necessary as a means for retain- 

 ing knowledge, hut because nothing else so 

 effectually opens the mind for the perception 

 even of the simplest evidences of a subject. 



(In the final examination in elementary me- 

 chanics above referred to, the following note 

 was appended to one of the questions: 



A redundant or wrongly used word in answer 

 to this question will be graded zero, 



and a day or two after the examination a 

 member of the faculty {not a professor of 

 mathematics) quoted this note in derision, as 

 if the only precision were numerical preci- 

 sion! May the shade of William Whewell 

 protect us!) 



In order to be able to define in a general 

 way the perceptive phase of the physical sci- 

 ences, let me distinguish two chief results of 

 the scientific activity of the nineteenth cen- 

 tury, namely, (1) an accumulated mass of 

 fact, under which heading I would include all 

 of the details of applied science, for indeed the 

 most important and compelling facts that have 

 been accumulated by the sciences are the facts 

 which are incorporated in the settled doings of 

 men, and (2) an established mode of thought 

 and inquiry which may be designated, using a 

 suggestive phrase of Bacon's, as " A new 

 engine, or a help to the mind corresponding 

 to tools for the hand." Here is an idea three 

 hundred years old ! 



We continually force upon the extremely 

 meager data which are obtained directly 

 through our senses an interpretation which in 

 its complexity and penetration would seem to 

 be entirely incommensurate with the given 

 data, and the possibility of this forced in- 

 terpretation depends upon the use of two com- 

 plexes, (a) a logical structure, that is to say. 



