These canoes are all poled about the lakes and canals; and I do not think we saw an Indian oar or paddle in the whole valley of Mexico.

In the ancient picture-writings, however, the Indians are paddling their canoes with a kind of oar, shaped at the end like one of our fire-shovels.

But, as we have seen, the distribution of land and water has altered since those days; and the lakes, far greater in extent, were of course several feet deeper all over the present beds; and even at a short distance from the city poling would have been impossible.

I suspect that the Aztecs originally used both poles and paddles, and that the latter went out of use when the water became shallow enough for the pole to serve all purposes.

Otherwise, we must suppose that the Mexicans, since the Spanish Conquest, introduced a new invention; which is not easy to believe.
We had first to get out of the canal, and fairly out into the lake.
This was the more desirable, as the canal is one of the drains of the city, an office that it fills badly enough, seeing that there is scarcely any fall of water from the lower quarters of the city to the lake.