3538 
extent to which we can rely upon them for further instruction, can 
only be estimated by a study of such exact experiments as have been 
made at the experiment stations throughout this country and Europe. 
Some illustrations of this matter are given by C. S. Plumb, under the 
title of the “ Fallacies of plat experimentation ” (Agr. Sci., Vol. II, 
p. 4), to which I will add the following remarks. Two sets of meas- 
ures are taken from the results of the year 1887 at Geneva, N. Y. 
The plats were arranged in two series, or two fields, but were in every 
respect as much alike as possible and supposed to be identical. The 
harvests from the respective plats were as follows: 
Weight of good | Weight of good 
Plat. ears. | Plat. ears. 
Series C. Series E. | Series C.| Series E. 
Pounds. | Pounds. | Pounds. | Pounds. 
CY A 8 Bie tena pe fll ge Wo SC MA Be ees Ue Uae ee 172.8 177.5 
Ds ee Se ae | 224.2 PAUSE) GI a ts SS Ce BAN Ne AE Rae ee | 171.8 167.1 
i St al ah ey AR a en 222.7 QUE OF) phG eae dee tern Ween eS 172.6 182.2 
MRNA IR, Le 5G gs 4 Led PAPNOKA 2201 WAT eye Le eas GEE 2 rel 183. 4 150.1 
io. ot Reet a eee ee earoedeoull Pe TOG IE lige re. fee acer cae en a \Patienn ts 140.2 
Ge Se ee COI de AC A an a etd, ee me PAAR 128.2 
gE) ama} au’s |) Averaessee ae 
eee ane |) peeeae 197.6 | Yield per acre_____ bushels_- 51.1 45.7 
NO ceeoe asics Seenesetee Sacco 243.8 186.0 || Number of plants..._.-___-. 12,380 12, 320 
WL oo sons se Seas este Sone | 224.6 168.1 | Number of good ears..__-..| 12,180 11, 400 
irae teas ae Ee Saves 3 Ht tw eee 209.0 169.1 || 
epipets te, FD ar nd | 191.7 | 177.6 || 
| 
The individual differences between these 36 plats simply show that 
the conditions were not so uniform as the aythor supposed; in fact, 
the regular gradations from the high numbers at the top of the column 
to the low ones at the bottom show that there was a slight systematic 
difference among the plats in each series. On the other hand, the 
decided apparent differences between the two series, as well as between 
the plats, is very largely of the nature of those differences that are 
called accidental in the theory of exact measurements. Similar dif- 
erences 1n a long series of observations of the temperature or the rain- 
fall of any locality are spoken of not as accidental error but as the 
variability of the climate, and these differences in the present case 
may properly be treated as variability in the productive power of any 
plat compared with the neighboring plat without for the moment 
inquiring as to the cause of this variability. But the mathematical 
theory of probabilities, or chance, or errors of observation, is equally 
applicable to this question of variability due to unknown influences. 
According to that theory we obtain the index of variability if we take 
the difference between the average of a series and the individual num- 
2667—05 M 23 
