THE PROBLEM SOLVED. XV 



and which is not so easily explained. If a horse is running at the 

 rate of a mile in 1:40, and he strides two hundred and sixty-five 

 inches, it is easy to determine the number of times ejvch leg is moved, 

 A timing-watch, tape-line, pencil, paper, and a little arithmetical 

 knowledge are all that are necessarv. 



The position of the feet have been noted. "We have seen that the 

 fore foot left the ground when it was almost as far back as the loin, 

 drawn up and thrown forward until struck again under the nose. 

 The celerity of this movement is almost beyond calculation, and until 

 Mr. Muybridge perfected his machinery there was a confused blur. 

 The plates had to be made so "sensitive" that the shadow of a can- 

 non-hall would be transfixed as it flew past, and Jove invoked to 

 lend his lightning to open and close the slides which guarded the 

 plates from contamination until the moment arrived, when the gro- 

 tesque pictures could be produced with defined outlines. I will not 

 venture at pi-esent on an estimate of the rapidity with which the feet 

 are moved. That it is fast, all will admit who will give any thought 

 to the subject. 



Here is the key to the answer. In this lies the solution of the 

 problem of the acceleration of the speed in the race-horse when shoes 

 are replaced with plates — in this the vindication of the old proverl) 

 "that an ounce on the heel is worse than a pound on the back." 



And now we will try an experiment : I take a cane, the length of 

 the fore leg of a horse. It weighs eight ounces — one foot of the 

 upper end balancing the other two feet. I move it through the air 

 with ease, bringing it from a resting position into fast motion as 

 quickly as I can, and I can stop it at the end of the circuit without 

 expending a great deal of force. I reverse it, placing the heavy end 

 on the floor. It not only requires a good deal more force to over- 

 come the inertia, but more accordingly to stop it when it reaches the 

 desired i)oint. I can switch it without fatigue for some time — when 

 clubbed it soon tires the muscles. 



Fatigue has the effect to cause a sharper action of the muscles. 

 When a horse is tiring, he commences to labor. The smooth, clean 

 action is lost, and he "clambers," "sprawls," and then "goes all 

 abroad." The horse when fresh has carried his rider, as the old 



