ZZ 
INTRODUCTION 
49. No student of commercial geography can be unaware how 
many subjects there are that still await investigation, and in many 
cases how far the means for obtaining the desired information are 
lacking. This deficiency is felt in a peculiar degree with regard to 
the trade and more particularly the home trade of our own country, 
but in all countries one has often to regret that the available data refer 
to the country as a whole instead of particular regions which it would 
be desirable to investigate. It may be useful to conclude this intro- 
duction with the enumeration of a few subjects for research, but for 
the reason just mentioned the labour involved in procuring the 
necessary data for the investigation of some of these subjects might in 
some cases be so considerable as to render it impracticable for the 
present to arrive at any satisfactory conclusions :— 
How far British rule in different parts of the world has contributed 
bo the growth of the trade of foreign countries. 
The relation between fluctuations in different meteorological 
conditions and the yield of various important commodities. The 
occurrence of frost, snow; hail, and fog, and the precise seasonal dis- 
tribution of rainfall (see 64-68, and p. 608, n. 92) and sunshine (356-62) 
may all have to be taken into account. 
The conditions of commercially successful and unsuccessful irriga- 
tion. 
The trade between countries of the temperate zones as contrasted 
with that between the temperate and torrid zones. 
The advantages of rural and urban centres for different kinds of 
manufacturing industry. 
The effect on commerce of the construction of particular rail- 
Ways. 
The difference in the nature and volume of traffic resulting from 
the substitution of railways through mountain tunnels for cart or 
sumpter traffic across mountain passes. 
The relation of seaports to their hinderlands. 
The influence on commerce of the possession by different countries 
of bulky commodities such as coal. timber, salt, ice, cement, wool, 
grain, and the like. 
The distribution of ocean traffic between sailers and steamers. 
The significance of changes in the value of imports and exports 
per head of population. 
The effect of local labour, local supplies of raw material, and local 
markets in the development of manufacturing industries. 
The ultimate destination of the bulk of the produce of particular 
1istricts, distinguishing home and foreign markets and the particular 
parts of foreign countries which form those markets. 
The exhaustibility of natural advantages for any particular kind of 
production, as evidenced by a rapid followed by a slower expansion of 
a local industry concerned in such production.