The Chagres was both the savior and the enemy of the builders of the Panama Canal. Before railroads were built, the Chagres was the route used by travelers going from the East Coast to California by way of Panama. It was a long, peaceful river, extending almost all the way across the isthmus, and would have made a perfect basis for a canal, but for one thing: in the wet season it could become a roaring torrent, regularly rising 30-40 feet above its dry-season levels after a major storm. So, while the river could be used as the source of all the water for the canal, it also needed to be tamed by flood-control dams if the canal was not to be completely inundated during the wet season.

The solution was to dam the river six miles from its mouth at a town called Gatun and simply flood the entire center of the country. This formed Lake Gatun, at the time the largest artificial lake in the world, providing more than 20 miles of navigation for the ships crossing the isthmus, as well as supplying all the water needed for the locks. Then, instead of using the lower Chagres as part of the canal, the canal engineers used it as a spillway for excess run-off water, mainly during the wet season.

This solution meant that the lower Chagres was left completely in its natural state - there is not a single building on the river, from the dam to the Caribbean, and the whole stretch of 6 miles or so is a national park, with no hunting or taking of plants allowed. The jungle presses in on both banks, but the river itself is about 200 yards wide and almost 40 feet deep for most of its length. So, great cruising (motoring, not sailing) for us! The wet season hadn't kicked in yet, so there was just a slow current - and in fact the river was tidal all the way up to the dam.

Our first full day on the Chagres, we puttered upriver, keeping an eye out all the while for crocodiles, monkeys, parrots, and sloths. We saw (and heard) plenty of noisy parrots, but nothing else. After motoring up until we could see the dam, we turned around and anchored around a bend, just out of sight of it and of other signs of human activity.

We were immediately serenaded by troops of howler monkeys. They sounded numerous and close, and were certainly loud! The howls frequently begin with three or four loud "Hup" sounds, followed by a chorus of mixed tenor and bass, which echo through the jungle. Our best analogy for the "Hup" is the deep barking of a dog, while the chorus sounds vaguely like the distant roar from a football stadium when the home team has just scored. It sounds as if there must be hundreds of monkeys participating, but later experience showed that there were only a few - a dozen at most. A single howling episode goes on for less than a minute. We have no idea why they do it, but there's one thing we're sure of: they howl every time it begins to rain. Given that this is one of the rainiest places on earth, we think it's a good thing Darwin didn't know about these monkeys -- he might have had second thoughts about evolution.

By the time we were anchored and tidied up, the howling had stopped completely; but we decided to go ashore anyway, and see what we could see. There was a small dock by the water's edge, and we tied our dinghy there and went ashore. No more than 50 feet down the jungle path, we looked up in the trees and saw six monkeys, apparently taking early naps. They were no doubt exhausted after all that howling! Their napping style was to lie on large branches of trees, with their bodies aligned with the branches and their arms and legs dangling down. Some steadied themselves with their prehensile tails clutching the branch or nearby vines. Interesting, but not howlingly. We tried howling a little at them, but all we got was sleepy looks.

We left the monkeys to their naps and hiked the path along the riverside. All around us were strange flowers, insects, and birds - and one big spider. There was en enormous variety of trees; to our untrained eyes, no two were of the same species. Down at our level, there were lots of tall ferns and stalks with huge leaves; 20 or so feet above us were the tops of numerous deciduous trees; then 80 feet or more above that were the tops of huge trees, some of them with trunks 10 feet or more in diameter. We felt as if we were deep in the Amazon, until we looked out to the east and saw the shimmer of Lake Gatun, and listened for the low throb of ship engines. The Gatun locks of the Panama Canal were only about half a mile away - but in a different world!

We returned to Akka for lunch and a swim (keeping an eye out for those crocs). Later that afternoon, the howling started again, first at some place downriver and then, like a call and response routine, directly inland from the little dock near us. We leapt into the dinghy and motored to shore. The howling stopped as we tied up, but we knew where the monkeys had to be. Sure enough, we found three or four of them swinging through the trees overhead - probably the same ones we'd seen before, but awake now. They moved smoothly from branch to branch and tree to tree, sometimes using their tails to hold on as they swung down to another branch, sometimes simply leaping into midair then catching a new branch as they fell. When going from tree to tree, they frequently ran out from the trunks until the branches bent under their weight, then leaped and landed on another branch that bent the same way.

But still no howling. We stood, watching, as the little troupe disappeared behind some foliage. Well, we figured, that was it. We had just turned to leave when the howling started again. We could see some of the monkeys, who appeared to be motionless; but we couldn't see them well enough to determine whether they were facing some other tribe or merely celebrating their arrival at their favorite berry bush or something like that.

Next day, we moved downriver about halfway to the mouth, again inspecting the towering forest for interesting life, with no sightings of crocodiles or any other of the jungle species we had been told to expect. We anchored at the spot nearest the Smithsonian Tropical Research Institute, which features a 165-foot construction crane that sticks out above the top canopy. Our cruising guide suggested a hike to the Center, saying that the heavy high canopy prevented underbrush, so you could walk easily - but remember to bring a compass, as it's easy to get lost. The guide also showed a little topographical map of the area around the crane, and we also had a chart of the whole area, which we traced from the laptop onto a piece of graph paper.

The crane was only about a half mile away through the jungle; the problem was that there was a 400-foot hill between it and us. The cruising guide offered no advice about how to finesse this bump, and the near face seemed almost too steep to climb. However, a little creek ran along one side of it, so we decided to go up the creek in the dinghy, get to the relatively flat land on the back side, then hike to the crane.

The dinghy ride was easy, but eventually a downed tree barred the way, so we left the dinghy about 0.6 nautical miles from the crane (we had our handheld GPS with us) and started to hike.

The cruising guide had lied to us about the underbrush.

We trudged about 600 feet, more or less in the right direction, through mud and dry creek beds, untangling vines from our bodies and legs at every step. Due to the dense foliage, we saw nothing of interest. Finally, Andi, who was in the lead, accidentally brushed against a rotten tree branch, which disintegrated. It turned out to be full of ants, which poured down over her head and shoulders. She screamed and started to try to brush them off, and of course all the while she was standing on the anthill at the bottom of that tree, so ants were climbing up her legs. She stepped out into the open and tried to kill all the ants, which were by now inside her shirt and pants. She finally succeeded, but not before receiving numerous bites; fortunately, these were not fire ants, and the bites never festered. But that was pretty much the end of our hike. We returned surprisingly easily to the dinghy and went back to Akka.

That afternoon, we decided to try to go over the top of the hill. The rainforest there was much more dense than where we'd been hiking that morning, and the underbrush appeared to be more manageable. Our plan was to go diagonally around the hill, rather than climbing the face in front of us. The straight-line distance was exactly .5 miles, according to our GPS.

We tied the dinghy at a place that had clearly been used by other boats - there were even a couple of tires rigged to keep boats off the rocky landing - and proceeded up the hill. And up the hill. And farther up the hill. The problem with ascending diagonally, as we had planned, was that the hillside was scored with deep ravines running straight downhill to the river. So unless we wanted to climb down into these ravines and then scale the far sides, we had no alternative but straight up. We were reassured by repeated indications of other climbers - a piece of rotten line rigged to help climb a 4-foot rock cliff, red and blue paint on various trees, etc.

After more than two hours of climbing, we reached the top (we think). But time was running out and we were still .4 miles from the crane. Even at an accelerated rate of progress (which we could not count on) it would be at least another hour to the crane, and then another couple of hours back to Akka, assuming we didn't get lost. At 4:00 PM, this seemed pretty dangerous (the sun sets at about 6:30 p.m. at this latitude), so we turned back.

We didn't get lost, not really, but we did stop repeatedly to examine cliffs below us and try to see how to descend them. It turns out it's a lot easier to see how to climb up cliffs when you're looking at them from the bottom than to see how to climb down when you're at the top! We pretty much ended up following the route we had taken up the hill, continually encountering landmarks we had noted on the way up. It took us only an hour to slide and scramble down the hill, but it took another half hour to get all the mud out of our boots!

We did see some more monkeys on the way up, and when they had swung their way from tree to tree into the distance, the howling started up again. This time we couldn't even see glimpses of them. On the other hand, a beautiful white hawk was flushed out by the monkeys and alighted on a branch only a few feet away from us. We have no idea what it was, and before we could get our camera out, it flew away.

So, Chagres detections stand at: Monkeys: 12 or so. Howling, beyond counting, but never howling while clearly sighted. Parrots: hundreds, all cackling to each other. Poisonous-looking jungle toad: 1. Beautiful butterflies: 3. Crocodiles: 0. Sloths: 0. Construction Cranes: 0. Ants: 1,000,000 or so.