86 Lf. E. Nipher—LKvolution of American Trotting- Horse. 
ArT. X.—The Evolution of the Americun Trotting-Horse; by 
RANCIS H. NIPHER. 
SINCE my paper in the July number of this Journal was 
written, I have calculated the constants in the differential equa- 
tion by mathematical methods, and have obtained a result 
differmg slightly from that given in the July number. The 
most probable value for the minimum time of trotting a mile 
turns out to be 91 seconds, instead of 93 seconds as was obtained 
by graphical methods. 
The final equation is 
log (s—91) = 1-703—0-0046 T, 
where s is the time (in seconds) of trotting a mile, and T is esti- 
mated in years from 1860. 
This equation does not give essentially different results from 
the former one, the only point of interest being in the new 
value for the limiting time. The probable error of this value 
is not over four seconds, and it is not likely that the running 
horse will beat his present record by five seconds, so that it is 
very probable that the trotter will finally surpass the running 
orse. 7 
This conclusion does not rest solely on mathematical evi- 
dence. The trotter carries his body more steadily—with less of 
rise and fall—than the runner, and it seems very reasonable that 
this should result to the advantage of the trotter, when the pro- 
cess of developing and adjusting his muscles and chest shall 
have been sufficiently carried on, so that the contest between 
the two animals shall have been reduced to a matter of muscular 
capacity. 
It is well known that some herds of wild horses on the Texas 
