MEASUREMENT OF VARIABLE PROPERTIES 155 



But since errors are committed with pipette B, the effects of 

 the cause (volume) B are continually varying according to the 

 law of errors (§ io8) and the increase of the volume given by B 

 is no longer regular, but varying continually. If the greatest 



1 n HI ]v V VI VII vjif jx X t 



Fig. 20. — The distance between each small dot and ot is supposed to 

 represent the volume of a portion. The thick dots represent the 

 curve of growth (see text) ; ot, time ; o, origin 



errors are supposed to be +o-io and -o-io c.c, irregularities 

 may occur in the following way : — the volume of portion 30 

 (for instance) is expected to be (without error) 19-29 c.c. ; if the 

 error is, for instance, +o-o6, the observed volume becomes 

 19-35. The volume of portion 31 is expected to be 19 30 ; if 

 the error is -o-io, the volume is reduced to 19-20. More or 



