By Student 23 
The average gain by the vise of sulphate of potash was 15'2.5 ewt. and the 
S.D. 9 cwt., whence, if we want the odds that the conclusion given below is right, 
z = 1"7 corresponding, when n = 4, to = "9698 or odds of 32 : 1 ; this is midway 
between the odds in the former example. Dr Voelcker says ' It may now fairly be 
concluded that for the potato crop on light land 1 cwt. per acre of sulphate of 
potash is a better dressing than kainit.' 
As an example of how the tables should be used with caution, I take the 
following pot culture experiments to test whether it made any difference whether 
large or small seeds were sown. 
Illustration III. In 1899 .and in 1903 " head corn " and " tail corn " were taken 
from the same bulks of barley and sown in pots. The yields in grammes wei'e 
as follows : 
189!) 1903 
Large seed 13 '9 7 '3 
Small seed 14'4 8'7 
+^ +-6 
The avei'age gain is thus "55 and the s.u. "Oo, giving z=l\. Now the table 
for ?i = 2 is not given, but if we look up the angle whose tangent is 11 in 
Chambers' tables, 
tan-^ll . 84° 47' . 
^ = -W~ + "'^T80-+"-' = "^^^' 
so that the odds are about 33 : 1 that small corn gives a better yield than large. 
These odds are those which would be laid, and laid rightly, by a man whose only 
knowledge of the matter was contained in the two experiments. Anyone con- 
versant with pot culture would however know that the difference between the two 
results would generally be greater and would correspondingly moderate the 
certainty of his conclusion. In point of fact a large scale experiment confirmed 
the result, the small corn yielding about 15 per cent, more than the large. 
I will conclude with an example which comes beyond the range of the tables, 
there being eleven experiments. 
To test whether it is of advantage to kiln-dry barley seed before sowing, seven 
varieties of barley were sown (both kiln-dried and not kiln-dried) in 1899 and four 
in 1900 ; the results are given in the table. 
It will be noticed that the kiln-dried seed gave on an average the larger yield 
of corn and straw, but that the quality was almost always inferior. At first sight 
this might be supposed to be due to superior germinating power in the kiln-dried 
seed, but my farming friends tell me that the effect of this would be that the 
kiln-dried seed would produce the better quality barley. Dr Voelcker draws the 
conclusion " In such seasons as 1899 and 1900 there is no particular advantage in 
kiln-drying before sovving." Our examination completely justifies this and adds 
