What a day of excitement that was!  We always thought we needed a certain amount of thrills to make life sufficiently interesting for us.  In a few hours’ time, in the central portion of Cataract Canyon, we experienced nearly enough thrills to last us a lifetime.  In one or two of the upper canyons we thought we were running rapids.  Now we were learning what rapids really were.  No sooner were we through one than another presented itself.  At each of them we climbed along the boulder-strewn shores—­the lower slopes growing steeper, the walls above towering higher—­clear to the end of the rapid.  Looking upstream we could pick out the submerged rocks hidden in the muddy water, and looking like an innocent wave from above.  Twice we had picked out channels in sharp drops, after carefully observing their actions and deciding they were free from obstructions, when suddenly the waves would part for an instant and disclose a hidden rock—­in one case as sharp as a hound’s tooth—­sure disaster if we ever struck it.  As soon as we had decided on a channel we would lose no time in getting back to our boats and running it for we could feel our courage oozing from our finger tips with each second’s delay.  Time and again we got through just by a scratch.  Success bred confidence; I distinctly remember feeling that water alone would not upset the boat; that it would take a collision with a rock to do it.  And each time we got through.  Twice I almost had reason to reverse my impression of the power of water.  First the stern rose up in front of me, as if squaring off at the tops of the cliffs, then descended, until it seemed to be trying to plumb the depths of the river.  The waves, rolling over me, almost knocked me out of the boat, I lost my hold on the oars and grabbed the sides of the boat; then, regaining the oars, I finished the run by pulling with the bow headed downstream, for the boat had “swapped ends” in the interval, and was heavy with about three barrels of water in the cockpit.  I bailed out with a grocery box, kept under the seat for that purpose.  It had been growing quite cold, and Emery’s indisposition—­or what was really acute indigestion—­had weakened him for the past two days, but he pluckily declined to stop.  I was soaked with my last immersion and chilled with the wind, so concluded there was no use having him go through the same experience and I ran his boat while he made a picture.  We were both ready to camp then, but there was no suitable place and we had to push on to the next rapid.  On looking it over we almost gave up our intention of running it.  It was about a fourth of a mile long; a mass of submerged rocks extended entirely across the river; the entire rapid seemed impossible.  We finally concluded it might be run by shooting up, stern first, on a sloping rock near the shore, then return as the current recoiled and ran back, dividing on either side of the rock.  The only clear channel was one about twelve feet wide, between this rock and the shore.  A projecting shore above prevented a direct entrance to this channel.