The big story flashes on the television screen, or commands several column inches of space in your newspaper. It cites an academic specialist who, materializing seemingly out of nowhere, is prepared to speak on the subject at hand, whether it be the economics of crude oil or the morality of euthanasia.

Well, the secret is out. Universities, colleges and think tanks produce directories of academic specialists who can speak to a seemingly infinite number of subjects, inviting reporters to call them. Yesterday's mail to Metro Scene contained a handy 92-page guide to such specialists at Georgetown University.

If this column (or any other reporter on GU's mailing list) needs to know about smoking, it can call Sol Katz, M.D., a professor of medicine, or Sorell L. Schwartz, PhD, a professor or pharmacology, and if it needs to know about quitting smoking, Michael J. Deboy, PhD, an assistant professor in the school of dentistry (smoking? dentistry?), is available.

Others are available to discuss, for example, necrotozing entercolitis (Lawrence J. Grylack, M.D.), Islamic fundamentalism (Barbara Freyer Stowasser, PhD), English and Irish history in the 19th and 20th centuries (the Rev. Jeffrey Von Arx, S.J., PhD), legal aid and indigent representation (Richard Carter, adjunct professor of law, and John R. Kramer, associate dean of law), and Soviet disinformation espionage (Roy Godson, PhD).

The list goes on. A reporter could spend a career and perhaps win a degree or two tuning in to GU's listing of press contacts. For the university, as one insider put it, the more mentions in the big media, the greater the perceived national reputation -- not that GU needs more than it already has earned. Taxing Land, Not Buildings

An organization called the League for Urban Land Conservation has been crying into the wind for several years with its proposals to use property taxes as an instrument for preserving and enhancing development in the Washington area.

Its main thrust, based on the theories of Henry George, is a tax on land, not "improvements" -- the buildings erected upon the land. If its proposals were adopted, the league contends, such problems as Metro financing and fares would be solved. Land near the subway, it asserts, is worth more than remote land.

The league's Walter Rybeck invited us the other evening to a forum at the Marriott Key Bridge Hotel where we heard a tantalizing -- if untested -- presentation by California state Assemblyman William J. Filante, who suggested a way to solve our problems.

Filante represents Marin County, a San Francisco suburb with -- can it be possible? -- more intense commuting congestion than the big-three counties surrounding Washington. Filante, who describes himself as "Mr. Benefit Assessment District," believes that property owners within, say, a half-mile of a transit line should pay a transit tax to absorb most or all of the transit system's subsidies. He wasn't prepared, however, to discuss the gradations between areas that receive frequent, around-the-clock transit service and those with only occasional rush-hour service, common there as well as here.

Alas, only one area legislator showed up for the thought-provoking meeting, Montgomery County Council member Neal Potter.