perched on a rock, are two rock pratincols. They are sleek birds, tiny, with beaks like stilettos. Their wings are black, their chests white. They have narrow bands of black across their eyes so that they look like a pair of Nike running shoes. According to the bird book these birds are typically found on rocks by fast moving bodies of water. Given the rate at which the water is running past this tiny island, the birds must think they have died and gone to bird heaven. What kind of speciation has transpired to place birds in a niche that says, "rocks with fast moving water?” Why are there no birds that prefer “rotting logs next to four lane highways?”There is a composite satellite photograph of the Earth at night. You can see the outlines of all the continents. Strikingly, you see what parts of the world are lit up. This map, more than any novel I have ever read, points up the aptness of the phrase "darkest Africa." The continent is virtually a blackout, save for a few spots around the edges and one great exception: at the top of the continent, like a rip in a blackout curtain, is the River Nile. It extends from the Nile Delta at the Mediterranean all the way through the center of Egypt. If this map shows the aptness of the phrase "darkest Africa," it does likewise for “White Nile.” At the southernmost boundary of Egypt, the strip of light comes to an end. The river, of course, does not. The difference is that in Egypt the Nile primarily services people while in Africa it primarily services animals. Only people need light.
This afternoon we drive to the top of Murchison Falls. There is still enough of the day left to watch the Nile being forced into a narrow gorge, 70 meters across, and then twist, writhe, crash and tumble 45 meters to the river below. This is the greatest amount of w
ater rushing through a small channel of any place in the world. It makes me think of the Bernoulli Principle, which states that any volume pushed through a narrow opening increases in velocity. That is why the water is moving so fast here. Substitute air for water and the larynx for the gorge at Murchison Falls and you have an explanation for how human beings are able to speak. The Bernoulli Principle is what makes the vocal folds open and shut a 100 times a second, faster in women because their folds are typically shorter. The roar of the river through the gorge is literally the river’s voice.Click here to listen to this entry in audio
