118 



Professor H. S. Hele-Shaiv 



[March 31, 



which have never been beaten ; while for one distance, that of 200 

 yards, the record of Seward in 1847, or sixty-four years ago, still 

 stands. In fact, a study of all the records of twenty-five distances 

 shows that several of them remain unbroken after comparatively long 

 periods, viz. from a quarter to half a century. 



Thus, so far as his own unaided powers of locomotion are con- 

 cerned, man may be considered, for all practical purposes, to have 

 reached long ago the limit of speed possibility. From earliest times, 

 however, he has brought the musculai" effort of other animals into 

 his service, and has devoted his intellect towards improving their 

 speed for his own uses. You will see graphically recorded in Fig. 1 



1870 



1675 



1885 



1890 



1895 



1880 

 rtlAR 



Fig. 1. — Derby Winners for 55 Years. 



the speeds of all the Derby winners from the year 1856, i.e. for more 

 than half a century. The average speed, which may be taken as 

 somewhere above 30 miles an hour, has doubtless slightly increased, 

 but it will be seen from the dotted line which has been drawn at the 

 top of the maximum speeds what comparatively little increase has 

 been obtained for an expenditure of the many millions represented 

 directly and indirectly in the training and breeding of these horses, 

 and it may be reasonably assumed that here again the limit has been 

 reached for the fleetest animal, by the aid of which man can increase 

 his speed of locomotion by using muscular power other than his own. 

 What, then, are the physical reasons for this limitation ? It is 

 not due to the chief cause, which we shall see later puts a practical 

 limit to very high speeds in mechanical locomotion, namely, the 



