MANURING OF POTATOES. 439 

experiments were conducted during the years 1897 and 
1898 by the Agricultural Department of the Glasgow 
Technical College, and in 1899 by the West of Scotland 
Agricultural College, into which the former Department 
had been merged. These experiments were carried out 
on twelve farms in 1897, en nineteen farms in 1898, 
and on seventeen farms in 1899, and the published reports 
on them were prepared by the present writer. In all 
cases where the experiments were conducted on more farms 
than one, the reports have been based mainly on the 
average results, and it is the generally accepted opinion that 
the average results of a sufficient number of properly conducted 
field experiments are of much greater value than those of 
any single experiment. In dealing with these various experi- 
ments and the reports on them, the series reported on by 
Professor Somerville, Mr. Solomon, and Mr. Lawrence will 
for the sake of convenience be referred to as the “ Durham” 
experiments; those reported on in the Yorkshire College 
publications by Professor Somerville and Professor Campbell, 
as the “Yorkshire” experiments; those reported on by Principal! 
Gordon as the “Cheshire” experiments; while the Scotch series 
will be designated the “ Glasgow ” 
It is in some respects untortunate that the various series 
experiments. 
of experiments were designed independently of each other. 
Had the same schemes been adopted at all the centres, 
strong confirmation would have been afforded of results 
obtained on all alike, while consistent variations would have 
thrown light on the influence exercised on the results by 
differences in climate and in soil. On the other hand, the 
separate schemes that have been adopted have admitted of 
inquiry into a much greater number of questions than could 
have been overtaken in any single experiment jointly carried 
out by all the Colleges, while the variations in the plans 
followed have not been so wide as to preclude useful com- 
parisons of many of the results. 
Influence of Vartety. 
The chief object aimed at in most of these experiments has 
been to discover the cheapest and most effective method of 
