792 



SCIENCE 



[N. S. Vol. XXX. No. 779 



similar proportion holds for the rest of the 

 indices. 



It will be noted that the topics omitted 

 in the new book are of the "practical" 

 type — annealing and artesian wells, while 

 most of those added in the new book treat 

 of unfamiliar subjects not likely to be met 

 with outside the physics laboratory — 

 spherical aberration, absolute temperature, 

 absolute units, air thermometer, Atwood 

 machine— topics of a highly specialized 

 type demanding the use of abstract, diffi- 

 cult, and to the pupils, unusual ideas for 

 their mastery. When we recall that the 

 teacher has just 11 minutes and 43.6 sec- 

 onds in which to make each topic clear to a 

 class of twenty or more, we need not be 

 surprised that the students find the subject 

 unintelligible, and that they carry away 

 only a rather confused jumble of words in 

 the place of clear, definite and usable 

 ideas. 



Because these technical topics are un- 

 familiar, the student does not see their 

 use or value— and many of them are use- 

 less to the majority of the pupils— so they 

 have no significance to him, and hence he 

 has no motive that impels him to study 

 them with enthusiasm. 



An example may help to make this point 

 clearer. In the early editions of Gage the 

 problems are of this type: "What amount 

 of work is required to raise fifty tons of 

 coal from a mine two hundred feet deep 1 ' ' 

 "Twelve hundred foot-pounds of energy 

 will raise a one-hundred-pound boy how 

 high, if none of it is wasted ? " In the 

 most recent books we find problems like 

 this: "How much work is done in lifting 

 a 10 kg. mass vertically 180 cm. 1 Give the 

 answer in kilogrammeters, in ergs and in 

 joules." "What force in dynes will lift 

 a masS' of five kg.? How many ergs of 

 work are done in lifting a mass of 5 kg. 20 

 cm.?" "A pull of one dyne acts for 3 



seconds on a mass of one gm. What 

 velocity does it impart?" Or again, in 

 the Rolfe and Gillett, Newton's second 

 lavv' of motion is stated thus: "A force 

 has the same effect in producing motion, 

 whether it acts on a body at rest or in mo- 

 tion, and whether it acts alone or with 

 other forces." 



The modei'n text states this: "Rate of 

 change of momentum is proportional to 

 the force acting, and takes place in the 

 direction in which the force acts." If we 

 did not understand Newton 's law, but were 

 trying to leai'n it for the first time, which 

 of these statements would be the more in- 

 telligible ? Which would leave vis with the 

 clearer and more usable idea? The latter 

 statement has been introduced for the sake 

 of greater rigor ; but taking it simply as an 

 English sentence, have we gained in rigor 

 by making the student memorize the state- 

 ment that a rate of change takes place in 

 a certain direction? This statement of the 

 law is what Carl Pearson in his ' ' Grammar 

 of Science" calls a metaphysical summer- 

 sault. And have we not thereby con- 

 verted the old and valuable "science of 

 things familiar" into a "nescience of 

 things familiar"? 



Hence the second important fact in the 

 development of the teaching of science is 

 that we have not only added to the number 

 of topics to be learned, but have also 

 changed the content of the old topics so as 

 to render them almost, if not entirely, un- 

 intelligible to beginners. Any one who 

 has taught classes of teachers in a summer 

 school, or has visited elementary classes in 

 physics, must have noticed that many of 

 the "laws and principles" of physics, as 

 they are expounded in the modern texts, 

 are none too intelligible to many of the 

 teachers themselves. How then can we ex- 

 pect to have the pupils leave their work with 

 clear, definite, usable ideas? This change 



