>Could anyone tell me when the projection rate of films began to >shift from 16 frames/s. to the now-standard 24 frames/s.?
The short answer is that sound required a standard fps and 24 ended up being the number. The better answer is that 16 fps was never standard despite a common perception that it was (even among silent-era cameramen according to Brownlow!). Silent films were shot at a variety of speeds and projected at a similar variety, with 16 being toward the slow end (though 12 fps wasn't uncommon). You can find a massive amount of documentation and discussion of this issue.
The one exception is that 16 fps was the standard for 16mm silent cameras and projectors during the 50s and up until sometime around 1964 when it shifted to 18 fps. Warhol's earliest films are at 16 fps but it's difficult nowadays to find a projector that can show them properly.
Screen-L is sponsored by the Telecommunication & Film Dept., the
University of Alabama: http://www.tcf.ua.edu