at time did not allow of an examination
of the other affluents of the Usayali trending towards San Ramon and
Tarmo.

On his return to Iquitos, Tucker was again dispatched to the United
States to procure another and smaller exploring steamer. During his
absence Captain James Henry Rochelle was directed by the Government at
Lima to take charge of the Hydrographical Commission as its acting
president.

After an absence of some months, Tucker returned to Iquitos with the
new steamer, which was named the _Mayro_, and was little more than a
large steam launch, intended for use where a vessel of greater draught
of water could not be employed.

The next expedition decided upon was for the exploration of the water
route towards Huanaco, by way of the entirely unknown river Pichis.
Most of the tributaries of the Ucayali had been traveled more or less
by the Jesuit priests from the College of Ocopa, but none of them had
attempted the route of the Pichis, the banks of which were in
possession of roving tribes of Indians, who permitted no stranger to
pass through their country. It was thought possible, and even
probable, from the stories told by the natives, that the head of the
Pichis river would be found well suited for being the eastern terminus
of the trans-Andean railway.

In February, 1873, the _Mayro_, with a detachment of the Commission on
board, was dispatched from Iquitos, with orders to await at the mouth
of the Pachitea river the coming of the _Tambo_. Tucker embarked on
board the _Tambo_ on the 1st of April with the main body of the
Commission, and arrived at the confluence of the Pachitea and Ucayali,
seven hundred and sixty-five miles from Iquitos, on the 13th of May.
The river had commenced to fall, which rendered it prudent not to
ascend the Pachitea in steamers, for had one of them got aground
whilst the water was falling, it would probably have remained in that
situation until the next annual rise of the river.

The water of the Amazon, and the same may be said of all its
tributaries, begins to rise about October, and continues to increase
its flood until December. In December there is a short period of no
rise, or perhaps even a slight fall, after which the river again
continues to rise until May, when the permanent fall commences and
continues until the following October, when the annual flood again
sets in. Sand bars are constantly forming and shifting in the channel
of the river, and for a steamer to ru