In 1952, the Ralph M. Parsons Company (an oil-refinery engineering firm that had done a good deal of work for Detrick), working with “Stanford scientists”—probably chemists William Perkins and/or Philip Leighton—sent plumes of zinc cadmium particles into the city’s air from aerosol generators mounted on trucks and installed on rooftops. … Camp Detrick had come up with a cover story, a fairly good one, printed in newspapers: General Creasy said that the Army had hired the Ralph M. Parsons Company to perform a series of twenty to thirty “smoke screen” tests, in order to learn more about how clouds of simulated smoke behave in different kinds of weather.

Nicholson Baker, Baseless- My Search for Sec…, loc. 267