THE CONQUEST OF TIME AND SPACE 



old stop-watch method. The nervous impulse through 

 which the mandate of the brain is conveyed to the hand, 

 and thus made to operate on the stop-watch, travels 

 along the nerve of the arm at the rate of not much 

 more than a hundred feet a second. The delay 

 thus involved, added to the time required for the 

 brain itself to act on the message from the eye, is dis- 

 tinctly appreciable, and every one is aware that indi- 

 viduals differ as to their reaction time. 



The practical result, therefore, is that timers are 

 often at variance to the extent of as much as two- 

 fifths of a second. Now in two-fifths of a second, as 

 we have seen, the record motor car covers a distance 

 of over 77 feet. Obviously such latitude in measure- 

 ment could not be permitted. Hence an electric de- 

 vice has been elaborated which tests the speed with 

 absolute accuracy, recording it automatically on a 

 strip of tape. Therefore the fractional seconds are 

 now stated in hundredths instead of in mere quarters 

 or fifths, and we may be confident — as we could not 

 always be regarding the old-time records — that the 

 different fractions of a second represent an actual 

 difference of speed. 



It may be of interest to make a further comparison 

 between the speed of the record automobile and the 

 fastest speed ever attained by a railway locomotive — 

 namely, a mile in thirty seconds. The gap is by no 

 means an insignificant one. A mile in thirty seconds 

 means 176 feet a second. This would allow the 

 champion automobile a lead of over seventeen feet 

 each second; and at the end of a mile the locomotive 



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