You can find almost anything in periodicals. Periodicals offer a breadth of materials unmatched by almost any other kind of source. Here are the kinds of things in periodicals that might be useful for your research in environmental history:

News or reportage tries to present a balanced, objective account of something notable that has happened recently somewhere in the world. Description of events will sometimes be accompanied by brief efforts to interpret or explain.
In opinion, commentary, or editorials, authors try to persuade their readers to agree with their viewpoint or to take some kind of action. The Federalist Papers, originally published in two New York newspapers, are a particularly good example. In some older newspapers, it might be difficult to tell the difference between commentary and news.

Periodicals are also great sources for financial news, since periodicals’ frequent publication allows them to provide the speedy and reliable information that is valuable in a marketplace. Some periodicals are devoted entirely to providing financial news, some contain separate business or financial news sections, and others simply note major events or trends in large markets (like changes in the Dow Jones Industrial Average or reports from the New York Stock Exchange).

• Periodicals often feature legal or commercial notices. These can record major property transactions, notices of upcoming sales, or announcements for public hearings, government meetings, or community-based civic events.
• Advertisements give periodicals another stream of revenue in addition to subscriptions. If you are curious about the history of marketing, periodicals are full of very useful sources.
• Some periodicals are entirely devoted to satire—writing that makes fun of some aspect of contemporary society—while other periodicals contain a humor section.
• Obituaries, marriage and birth notices, and social records often provide more details about these events that you can find in the basic legal records. Some periodicals have “society” pages that contain juicy gossip about local families and even report on big parties or celebrations. If you were writing about the environmental impact of exotic fashion in the 1920s, you might turn to a description of a fashionable party from that period for an anecdote that could help bring your data to life.
• Some periodicals also contain literature. Many famous novels from the nineteenth century were originally published serially, chapter by chapter, in periodical sources. In some cases, you may find that the serialized versions differ from the published novels. If you wanted to find out about the development of Charles Dickens’ views on urban pollution in London, for example, you could look at the periodicals where some of his novels first appeared.
• Periodicals also contain specialized content depending on their audience. You can find periodical sources written for almost any interest group. For environmental history research, newsletters for industry or advocacy groups can be valuable. Think about what you could learn from Sierra Club newsletters or old issues of Earth First!.
• Periodicals are also where you can find some of your best secondary sources, particularly scholarly articles written by previous researchers examining questions related to your own. In every field there are leading academic journals; ask a professor or librarian about the most influential periodicals in your field. Environmental historians should be familiar with Environmental History, American Historical Review, Journal of American History, and Isis.