Makch 24, 1922] 



SCIENCE 



317 



fort, in favor of it. The latter exhibited 

 standard text-books on zoology, and grew quite 

 excited as he quoted evolutionary statements 

 from them. 



A representative, whose vote against the bill 

 made it a tie, called up his pastor by long dis- 

 tance telephone, while the balloting was yet in 

 progress, and asked for advice as to how to 

 cast his final vote. 



The representative from Breathitt County, 

 one of the counties of the mountain section, 

 where anti-evolution sentiment is strong, sur- 

 prised everybody by voting against the bill; 

 indeed it was he who east the deciding ballot. 

 This county is known as "Bloody Breathitt," 

 because of its distinctive lead in homicides 

 growing out of private feuds. This member 

 can scarcely be said to represent the sentiment 

 on evolution in this county, which has an illit- 

 eracy of 21.6 per cent. It is doubtless more 

 correctly represented by the editor of the Jack- 

 son Neivs of that county, who recently said, 

 "The professors at the state university may 

 believe they are descended from apes and 

 baboons, but let it be known that the good 

 people of Breathitt are pure Anglo-Saxon." 



Arthur M. Miller, 

 Department of Geology, 

 TJNrvEESiTY OP Kentucky, 



IjEXINOTON, Ky. 



ROTERTIA 



In the mind of the student the word "mo- 

 ment" is unalterably connected with the idea 

 of a very short space of time. Such an ex- 

 pression as "moment of force" is, therefore, on 

 the face of it, meaningless. It is useless for 

 the teacher to point out that "moment" also 

 means importance, and that the moment of a 

 force is merely its importance or effectiveness 

 in producing rotation. Calling it a "moment 

 of force" makes "a tendency to produce rota- 

 tion" a difficult physical conception for the 

 student to grasp. This difficulty has been 

 recognized by teachers of physics, who have 

 at last very generally discarded the expression 

 "moment of force," in favor of the shorter, 

 simpler, and clearer term "torque." A torque 

 is a twist. There you have the whole thing in 



a nut-shell, and the student knows what you are 

 talking about. 



Whj"^ not keep up the good work by accept- 

 ing suitable substitutes for "moment of mo- 

 mentum" and "moment of inertia" as well? If 

 "moment of force" is bad, these are worse. 

 Some text-book writers have already seen the 

 wisdom of using "angular momentum" for 

 "moment of momentum." This is a distinct 

 improvement, since "angular momentum" car- 

 ries its meaning on its face. But so far I have 

 failed to find any serious attempt made to use 

 a substitute for "moment of inertia," although, 

 to my mind, this is the worst offender of the 

 three. The magnitude of a moment of force is 

 calculated by multiplying a force by a dis- 

 tance (f X r) ; similarly that of a moment of 

 momentum by multiplying a momentum by a 

 distance (mv x r) ; but the magnitude of a 

 moment of inertia is not equivalent to the pro- 

 duct of an inertia times a distance (m x r), 

 but times the square of a distance (m x r^). 

 The use of the word "moment" in aU three 

 cases, therefore, misleads the student to expect 

 an analogy which does not exist in the ease of 

 moment of inertia, thus making the term par- 

 ticularly inappropriate. My experience has 

 been that the word "rotertia" immediately con- 

 veys to a student the physical conception buried 

 in the expression "moment of inertia"; and in 

 such a way that it is not easily forgotten. I 

 therefore seriously urge its adoption. "Roter- 

 tia" on the face of it is equivalent to rotation- 

 al inertia ; and, hybrid though its stock may be, 

 what more can we demand of a technical term 

 than unambiguity, clarity, and force? 



Frederick Palmer, Jk. 

 Haverpord College, 



November 14, 1921. 



THE VALUE OF TILTH IN AGRICULTURE 



Dr. Jerome Alexander (in Science, Feb- 

 ruary 10, 1922) criticises a statement made by 

 the present writer (Science, September 2, 

 1921) that "the comminution of the surface 

 of the soil, more or less perfectly stops evapo- 

 ration and thus conserves the store of soil 

 water." This statement is said by Dr. Alex- 

 ander to be "quite contrary to all engineering 



