COMMERCIAL RELATIONS: THE GREAT LAKES 153 



connected with the life-saving station. Storm warnings are 

 usually displayed upon a tower, where they are visible from 

 vessels about to leave the harbor. Flags are used in the day 

 and lights at night. 



170. Other ports. Our study has been mainly a study of 

 the port of Chicago. As the largest city on the lakes and the 

 port closest to the heart of the country, it has particular inter- 

 est. A similar study might very well be made of any other 

 lake port or ocean port, and quite similar facts would be found 

 to account for its existence and growth. 



