In spite of this warning, I nearly came to grief at the dam.  The wind had shifted until it blew directly down the stream.  The river, nearly a mile wide, still ran with a powerful current; I ceased rowing and drifted down, over waves much like those one would find on a lake driven by a heavy wind.  I saw some high poles and a heavy electric cable stretched across the stream, and concluded that this was the beginning of the dam.  I began to look ahead for some sign of a barrier across the stream, far below, but I could see nothing of the kind; then as I neared the poles it suddenly dawned on me that there was no raised barrier which diverted all the water through a sluice, but a submerged dam, over which the flood poured, and that the poles were on that dam.

My sail-like sunshade was dropped as quickly as I could do it, and, grabbing the oars, I began to pull for the California shore.

It was fortunate for me that I happened to be comparatively near the shore when I began rowing.  As it was, I landed below the diverting canal, and about a hundred yards above the dam.  On examination the dam proved to be a slope about fifty feet long.  A man in charge of the machinery controlling the gates told me that the dam lacked seven feet of being a mile wide, and that approximately seven feet of water was going over the entire dam.

Great cement blocks and rocks had been dropped promiscuously below the dam to prevent it from being undermined.  Even without the rocks it was doubtful if an uncovered boat could go through without upsetting.  The great force of the water made a trough four or five feet lower than the river level, all water coming down the slope shooting underneath, while the river rolled back upstream.  On two occasions boatmen had been carried over the dam.  In each case the boat was wrecked, but the occupants were thrown out and escaped uninjured.  I could not help but be amused, and feel a little uncomfortable too, when I saw how nearly I came to being wrecked here, after having escaped that fate in the rapids of the canyons.

I ran my boat back to the diverting canal, then rowed down to the massive cement gates, which looked to me like a small replica of some of the locks on the Panama Canal.  With the help of an Indian who was ready for a job my boat was taken out, rolled around the buildings on some sections of pipe, and slid over the bank into the canal below the gates.

In spite of a desire to spend some time inspecting the machinery of this great work,—­which, with the canal and other improvements, had cost the government over a million dollars—­I immediately resumed my rowing.  It was mid-afternoon, and measured by the canal, which was direct, it was twelve miles to Yuma.  But I soon learned that great winding curves made it much farther by the river.  In some cases it nearly doubled back on itself.  The wind had shifted by this time and blew against me so hard that it was almost useless to attempt rowing.