growing louder and
nearer, and

"in half an hour a great wave several feet in height, could be
distinctly seen flashing and sparkling in the moonlight, extending from
one bank to the other and advancing swiftly upon us. While it was only a
few hundred yards distant, the ebb tide continued to flow by at the rate
of three miles an hour. A point of land and an exposed bar close under
our lee broke the wave into several long swells, and as these met the
ebb the broad sheet around us boiled up and foamed like the surface of
a cauldron, and then, with scarcely a moment of slack water, the whole
went whirling by in the opposite direction. In a few moments the low
rollers had passed the islands and united again in a single bank of
water, which swept up the narrowing channel with the thunder of a
cataract."

This was the great tidal bore once more, which, at the occurrence of the
spring tides, makes the entrance of the river extremely dangerous. It
is due to the narrowing of the Gulf of California forcing the tides
into close quarters, and its violence is augmented by collision with the
equally furious current of the Colorado. The battle between this tidal
wave and the Colorado continues for many miles, till at last the sea
tide gradually loses its power and succumbs to the flood of the river.*
The latter falls at the mouth, according to Ives, about thirty feet in
a few hours after the ebb begins. The shallower the water as the tide
rushes in against the ebb, the angrier the wave becomes, sometimes
reaching a height of ten or twelve feet.

* The tide ascends thirty-seven miles. Lowest stage of water about
three feet, average six feet, and highest about twenty feet.

At Robinson's Landing, a mere mud flat, a camp was established and
preparations made for the voyage to the extreme limit of navigation.
The parts of the steamer were put ashore and a suitable spot selected
whereon to set her up. The high tides were over for a month, and the
mud began to dry, enabling the party to pitch their tents. It was an
uncomfortable spot for expedition headquarters, but the best that could
be had, as the Monterey was not permitted by her owners to venture
farther up the river. But this delay, discomfort, and difficulty, to say
nothing of expense, might have been avoided could a contract have been
made with the existing steamboat company. As the bank on which the boat
was to be reconstructed was not likely to be overflowed more than