G ALTON AND STATISTICAL STUDY OF INHERITANCE 159 



enclosed. When the frame is held topsy-turvy, all the shot runs 

 to the upper end ; then when it is turned back into its working 

 position, the desired action commences. 



The shot passes through the funnel and, issuing from its 

 narrow end, scampers deviously down through the pins in a 

 curious and interesting way ; each one of them darting a step to 

 the right or left, as the case may be, every time it strikes a pin. 

 The pins are so placed that every shot strikes a pin in each 

 successive row. The cascade issuing from the funnel broadens 

 as it descends, and at length every shot finds itself caught in a 

 compartment immediately after freeing itself from the last row of 

 pins. The outline of the columns of shot that accumulate in the 

 successive compartments approximates to the mathematical law of 

 frequency, and is closely of the same shape, however often the 

 experiment is repeated. 



The outlines of the columns would become more nearly iden- 

 tical with the normal law of frequency if the rows of pins were 

 much more numerous, the shot smaller, and the compartments 

 narrower ; also, if a larger quantity of shot were used. 



The principle on which the action of the apparatus depends 

 is that a number of small accidents befalls each shot in its career. 

 In rare cases a long run of luck continues to favor the course 

 of a particular shot towards either outside place, but in the large 

 majority of instances the number of accidents that cause deviation 

 to the right balances in a greater or less degree those that cause 

 deviation to the left. Therefore most of the shot finds its way 

 into the compartments that are situated near to a perpendicular 

 line drawn from the outlet of the funnel, and the frequency with 

 which shots stray to different distances diminishes in a much 

 faster ratio than these distances increase. 



Types which are based upon vital statistics have peculiar interest, 

 since they persist from generation to generation, according to the 

 law of specific stability, while they also undergo slow changes 

 according to the law of the mutability of species. 



Individuals come and go, but the type persists, and its slow 

 changes may be pictured as quite independent of and more substan- 

 tial than the procession of individuals which files past only to vanish 

 from the world. 



