826 



SCIENCE 



[N. S. Vol. XXXVI. No. 937 



physicists who collectively have a wealth of 

 knowledge concerning gyroscopic action. Sup- 

 pose that twenty or more of these were each to 

 write an answer to the following question, 

 suppose that the answers showed substantial 

 agreement, would not their words come with 

 great authority and lead to a thorough in- 

 vestigation of the subject? 



The question which I propose for discus- 

 sion is this : 



7s it probable that the gyroscopic action of 

 a revolving-cylinder engine produces danger- 

 ous stresses upon the frameworh of the flying- 

 machine? 



Practical airmen are not in agreement in 

 this matter. Some say that the gyroscopic ac- 

 tion is negligible, others say the contrary. 



K physicists and others who have studied 

 the gyroscope will kindly respond to this sug- 

 gestion, I will see that marked copies of 

 Science are sent to the editors of the leading 

 aeronautical publications of the world. 



James Means 



Boston, 



November 22, 1912 



THE PEDOMETER 



To THE Editor of Science: In glancing 

 over some pages of the Encyclopedia Britan- 

 nica (eleventh edition) recently I found a 

 short article on the pedometer, the concluding 

 sentence of which is: 



Obviously the pedometer is little better than an 

 ingenious toy, depending even for rough measure- 

 ments on the uniformity of pace maintained 

 throughout the journey measured. 



Two definite statements are here made, 

 both of which are quite erroneous. When 

 properly understood and properly used the 

 pedometer is a most useful addition to the 

 outfit of a traveler and an especially delight- 

 ful and comforting companion to those who 

 know the joy of seeing the world a piede. A 

 cheap instrument (costing only a dollar) 

 which I have carried almost every hour of al- 

 most every day during the past dozen years is 

 still " as good as ever," registering distances 

 with an accuracy that is really surprising. It 

 has been tested over hundreds of miles and 



kilometers of roadway in England, Germany, 

 Italy and Switzerland (especially in the last- 

 named country, where on most highways every 

 kilometer of distance is marked by a stone 

 monument), and found correct generally 

 within one per cent., the error rarely being 

 as much as two per cent. I have known gov- 

 ernment surveys not so good. Such an in- 

 strument can hardly be classed with " in- 

 genious toys " and the explanation lies in the 

 fact that the remainder of the sentence 

 quoted above is equally erroneous. With the 

 right sort of pedometer within certain con- 

 siderable limits the record is not affected by 

 variation in length of pace. There are two 

 sorts of pedometers, the right sort and the 

 wrong sort, and unfortunately it is the vrrong 

 sort that is usually offered for sale. This is 

 simply a " step counter " the figures on the 

 dial showing the number of steps taken and it 

 is necessary to know the average length of step 

 to convert this record into distance. Aside 

 from the great inconvenience of being obliged 

 to make a calculation whenever one desires to 

 know the distance travelled even this instru- 

 ment when properly adjusted and calibrated 

 ought to give fairly satisfactory results. But 

 the right sort of pedometer is not a pace 

 counter and the numbers on the dial show di- 

 rectly the distance traversed in miles or, if 

 one has the good fortune to live in a country 

 where reason prevails over prejudice, in kilo- 

 meters. In this the movement of the register- 

 ing mechanism is caused by the rise and fall of 

 a kind of horizontal pendulum, the length of 

 the stroke for each step and hence the distance 

 registered being capable of adjustment. But 

 when short steps are taken the pendulum does 

 not pass through the whole arc of its possible 

 movement and the distance registered is con- 

 sequently less. Thus, as stated above, the 

 movement of the index hand is proportional 

 to the distance traversed and, within certain 

 limits, is not affected by variation in length of 

 step. This is a most important fact and gives 

 to this form of pedometer a value evidently 

 not generally known or appreciated. 

 Eavenna, Ohio, T. C. M. 



November 11, 1912 



