registered Speeds of American Trotting Horses. 313 



between 28 and 29 on the scale along the base. The dots are con- 

 nected by thin lines to show the trace or curve of the observations. 

 The smooth curves are those of normal frequency, calculated from 

 the values of the mean (M) and of the probable error (P.E.), which 

 are given in the diagrams. 



306ec? 20 io 



Leaving aside for the moment the strange pinnacle that rises on 

 the extreme left of every diagram, we see that the traces of the 

 observations run very roughly, but not intolerably so. In each 

 diagram they seem to be disposed about a fundamentally smooth 

 curve. Considering the smaliness of the interval, namely, only 

 1 second, that separates the observations assigned to each pair of suc- 

 cessive columns, together with the experience derived from other 

 kinds of statistical curves, it seems to me that the run of the obser- 



