INTRODUCTORY 
29 
tion. Our object is to bring out the stresses 
and strains which broadly account for things 
as they are. We only fully explain a thing 
when we have completely isolated all relevant 
and appreciable tendencies at work, and 
estimated their several influences. But behind 
many of the things to.be explained we discover 
a complicated system of tendencies within 
tendencies, some of which are long in bringing 
about their effects, and some of which would 
produce their effects in a short time were 
they not counteracted. In economics it is 
convenient, therefore, to distinguish between 
immediate tendencies, short period tendencies, 
and long period tendencies. The first are 
predominantly effective as regards immediate 
results. The second are those which are com 
paratively speedy in their operation. The 
third are the tendencies remaining. When 
in economics we ask what is the effect of a 
given cause we may mean by the effect, the 
immediate effect, the short-period effect, or 
the long-period effect. Let us take to illus 
trate the distinction a particular example. 
If the demand for steel increased, the 
immediate effect on price would be the 
resultant rise in the price of steel while 
the agents in production were left exactly 
as they were. The short-period effect would