It's not fair, I know, but when "Mountains of the Moon" concluded, it occurred to me that David Lean could have made a magnificent epic from this material.

As it is, director/co-writer Bob Rafelson has done well by it, but the film falls short of achieving the greatness he was obviously striving for.

Yet, how could he go too wrong with such an inherently fascinating story as this one about 19th-century explorer Richard Burton and his rivalry with former friend John Hanning Speke.

The film's shortcomings begin early, however. The first scenes introducing Burton and Speke start up without enough foundation, and those early moments are a bit confusing.

It does become more clear as we follow Speke and Burton, who are as opposite in their personalities as two people can be, after they meet and join forces for an ill-fated expedition in Africa (which provides the film's most brutally violent moments).

Eventually they are reunited for a fully equipped and funded Royal Geographic Society trip to find the source of the Nile river, the "mountains of the moon" as the natives call the remote inland area they seek.

The bulk of the film's first half chronicles their adventures and Burton's digressions as they head toward their goal, then the second half of the film focuses on the collapse of the relationship between Burton and Speke as their very different reasons for exploring become apparent.

Though the film's first half is obviously more flamboyant and provides more excitement, I found the second half much more interestingly dramatic. Though the entire film attempts to focus on the tenuous, perhaps homoerotic relationship between these two men, it is when they return to civilization and go their separate ways that the most compelling probing of their respective characters takes place.

And while Patrick Bergin and Iain Glen, the unknown actors chosen to play Burton and Speke, respectively, do very well, there's something missing from Bergin's interpretation of Burton. There's an essence, a power of screen presence that just doesn't come across here. Something that would certainly have helped make this larger-than-life adventurer seem more credible.

Burton was, after all, one of history's most diversified characters — an earthy intellectual with obsessions in many areas, ranging from the exploration of unknown geography to the collecting and translating of Eastern erotica.

And though "Mountains of the Moon" is certainly a rarity among modern movies in its scope and subject matter, the real question is not why make a movie about Burton at this point in time, but why haven't dozens of movies been made about Burton before now?