A strange episode in his career now occurs. Bolivar actually pressed him as a soldier; but Trevithick soon 'tir'd of war's alarms,' and the President readily allowed him to return to more congenial pursuits, sending him on some special mission to Bogota--yet not before Trevithick had signalized his connexion with the army by inventing a most ingenious carbine with an explosive bullet. Whilst in South America he also became, for the nonce, a surgeon, and actually amputated both legs of a poor fellow crushed by the fall of some of Trevithick's heavy machinery. The man was very proud of what he had undergone, and used to boast of his capital stumps. Having previously paid a short visit to Chili, Trevithick (who had now lost all his property) finally left Peru in 1822, on the above-named special mission; but, distrustful of Bolivar's promises and hearing of something more to his advantage, as he considered, he made his way to certain rich mines that he had heard of in Costa Rica instead. Thither--to that region of snakes, miasma, and earth-quakes--we must now follow him. There were known to be rich mines of the precious metals near Quebradahonda, in the interior of the little tract of mountainous country which forms part of the narrow belt of land connecting North and South America; but the difficulties of access in 1826-27 rendered them almost valueless, and Trevithick and his party conceived the idea of approaching them from the Atlantic side, by a route which should be practicable for steam conveyances--namely, by way of San Juan (now Greytown) and the rivers San Juan de Nicaragua and Serapique. Rafts and boats were constructed for the descent of those streams, and fearful hardships and dangers befell the explorers--who were bent upon accomplishing a somewhat similar task in Central America to that which Lander had performed a few years before in Western Africa. Three weeks were spent in accomplishing their object--during which the little party subsisted on monkeys and wild fruits; and more than once Trevithick, an indifferent swimmer, but who managed to buoy himself up by bundles of sticks which he placed under his arms, was nearly drowned. He had however, at length the gratification of reaching San Juan--the first European who had made the voyage from Lake Nicaragua to the sea. By some means or other he contrived to reach Cartagena (de las Indias) on his homeward journey, disconsolate enough no doubt; but what befell him on his way is best told in the following letter: 'Stanwick, Cumberland, 27th November, 1864. 'SIR,