Two new rivers were discovered by the Commission flowing into the Pichis. One of them was named the Trinidad, from having been discovered on Trinity Sunday, and the other was called Herrera-yacu, after Major Ramon Herrera, of the Peruvian Army, who commanded the escort of the Commission. The supplies of the expedition were running too short to allow of any but a cursory examination of these two rivers. The Trinidad, trending to the westward, can only be of value as affording a water route to the plains lying between the Pichis and the Ucayali, but it is possible that the Herrera-yacu may furnish a nearer water route to Cerro de Pasco than any yet known. Whilst the canoes of the Commission were descending the Pachitea, they were attacked by the Cashibos, who assembled on the banks of the river, and, waiting until the leading canoes had passed, let fly flights of arrows at the canoe which brought up the rear. The Cashibos were dispersed by a few rounds from the Remington rifles of the Commission, and the explorers met with no further forcible opposition on the way to the steamers awaiting them at the mouth of the Pachitea, where they arrived after a canoe voyage of forty-one days, during which many difficulties and some dangers were encountered and overcome. Not a single person under Tucker's command was killed, or died from sickness, during this expedition, and, singular to relate, after all the hardships and exposure endured the explorers were in much better health when they returned to their steamers than when they left them at the beginning of the expedition. On the 15th of July, 1873, the steamers _Tambo_ and _Mayro_, comprising the exploring squadron, reached Iquitos after an absence of three months and ten days. From the 15th of July to the 18th of September the Hydrographical Commission was on shore at Iquitos, employed making charts of the surveys of the late expedition, whilst the steamers were being refitted for further service.