INTERNATIONAL TRADE 151 
and when the conditions attending its use 
are so thoroughly known to him that he can, 
without much trouble and delay, take the 
requisite steps to protect it if prudence so 
dictates. Of course, we should be mistaken 
in saying that labour is absolutely immobile 
internationally. Labour flows from any centre 
all over the world, but it flows with less ease 
between places with different languages than 
between places with the same language, with 
less ease again between different empires than 
between regions forming parts of the same 
empire, and with less ease yet again between 
a country and its colonies than between 
different parts of the same country. Capital 
also overflows national boundaries, but only 
as a rule under the persuasion of a more 
than usually generous rate of interest ; and in 
so far as capital goes abroad, it will be found 
that its favourite investments are public 
securities, and such industrial stock as is 
closely related to them. 
As we have now formed a general idea of 
the problem of international exchange we 
may at once proceed to its detailed solution. 
It will be convenient to do so by laying down 
a series of propositions. The one which is 
logically the first is the following, that