MAYOR BARRY has combined some basic economics with a Metro subway map to come up with his own version of venture capital: he is venturing into the suburbs by rail to introduce supply to demand. There are jobs going begging in the suburbs and unemployed ready-to- work people in the District, and therein lie the makings of some constructive alliances. Having begun some projects already in Fairfax County, Mr. Barry hopped on the Red Line last week to meet with employers in Montgomery County -- and he came up with more good results.

As in Fairfax, one of the fast-growing industries in Montgomery is the hotel business. And one of the business leaders most interested in hiring workers from the District was James E. Beard, general manager of the Hyatt Regency Bethesda, which is slated to open next month -- with about 450 jobs to be filled. Foster Shannon, chairman of the Washington Metropolitan Area Jobs Council, noted that this regional approach to unemployment benefits all jurisdictions. A look at two numbers underscores the point: July unemployment in Montgomery was 2.4 percent while in the District it was 8.9 percent.

Other companies represented along the way included two hospitals, GEICO, Washington Gas, Pepco, C&P Telephone, the Gaithersburg Marriott, Coca-Cola, Vitro Laboratories and General Electric. Mr. Barry's offers of workers include training assistance, subsidizing of commuting costs and other help in meeting job orders. The Greater Washington Board of Trade is assisting in making connections, and there are more trips being planned by the mayor.

Obviously these ventures make economic sense. But there is a constructive side benefit as well. Suburban employers and District workers are learning more about each other these days -- and it's not bad at all.