As few of the automobile factories make all the parts of their machines, there are in Detroit many shops for the manufacture of steel, aluminium, and brass castings, and of gears, wheels, and various other automobile parts. Another of Detroit's important industries is the manufacture and repair of steam- and electric-railroad cars. These are largely freight cars, although many passenger cars are also made. Other lines of business include foundry and machine-shop products, the making of druggists' preparations, the manufacture of flour, the packing of beef and pork, and the preparation of other food stuffs. [Illustration: WHERE AUTOMOBILES ARE MADE] Then Detroit makes great quantities of soda ash and alkalies. This industry Detroit owes to the fact that here are found both limestone and salt, which is obtained from wells driven along the river bank. Both of these materials are required in the manufacture of soda ash. The printing-and-publishing business gives employment to thousands; so does the manufacture of paints and varnishes. In stoves, ranges, and furnaces, Detroit leads every other city in the country. It is interesting to know that Detroit makes great numbers of adding machines, that it is the largest producer of overalls in the country, that it is a center of the brass industry, that it turns out more than 300,000,000 cigars each year, and that it is one of the largest producers of wrought- and malleable-iron castings. The entire business of a city is, of course, never wholly manufacturing. Part of its business is always the distribution of things to supply the needs of its inhabitants and of the people who live in the surrounding country. When these goods are sold in large quantities to merchants who in turn sell them to the person using them, the business is known as a wholesale business. When they are sold by the merchant directly to the user, he does what is called a retail business. The wholesale business of Detroit is very large. Its merchants do the larger part of the wholesale business through the entire state of Michigan and in parts of northern Ohio, Indiana, Illinois, Wisconsin, and Minnesota. They even furnish certain supplies to some parts of Canada. Dry goods, drugs, hardware, and groceries are the principal things in which Detroit wholesalers deal. Detroit has also many large retail stores, which supply not only the people who live in the city of Detroit but those in the surrounding country as well. Thanks to the many suburban electric railroads and the many steam roads, the people who live in the smaller places are able to come to Detroit to purchase things they want. Now let us take our map again and notice the location of Detroit in relation to the rest of the country, for location, as you know, has very much to do with the growth of cities. [Illustration: THE DETROIT RIVER TUNNEL]