The Morrison Co.'s freighter _Vigilant_, bound from Valparaiso, arrived this morning at its wharf in Darling Harbour, having in tow the battled and disabled but heavily armed steam yacht _Alert_ of Dunedin, N. Z., which was sighted April 12th in S. Latitude 34° 21', W. Longitude 152° 17', with one living and one dead man aboard. The _Vigilant_ left Valparaiso March 25th, and on April 2d was driven considerably south of her course by exceptionally heavy storms and monster waves. On April 12th the derelict was sighted; and though apparently deserted, was found upon boarding to contain one survivor in a half-delirious condition and one man who had evidently been dead for more than a week. The living man was clutching a horrible stone idol of unknown origin, about a foot in height, regarding whose nature authorities at Sydney University, the Royal Society, and the Museum in College Street all profess complete bafflement, and which the survivor says he found in the cabin of the yacht, in a small carved shrine of common pattern. This man, after recovering his senses, told an exceedingly strange story of piracy and slaughter. He is Gustaf Johansen, a Norwegian of some intelligence, and had been second mate of the two-masted schooner _Emma_ of Auckland, which sailed for Callao February 20th, with a complement of eleven men. The _Emma_, he says, was delayed and thrown widely south of her course by the great storm of March 1st, and on March 22d, in S. Latitude 49° 51´, W. Longitude 128° 34´, encountered the _Alert_, manned by a queer and evil-looking crew of Kanakas and half-castes. Being ordered peremptorily to turn back, Capt. Collins refused; whereupon the strange crew began to fire savagely and without warning upon the schooner with a peculiarly heavy battery of brass cannon forming part of the yacht's equipment. The _Emma's_ men showed fight, says the survivor, and though the schooner began to sink from shots beneath the waterline they managed to heave alongside their enemy and board her, grappling with the savage crew on the yacht's deck, and being forced to kill them all, the number being slightly superior, because of their particularly abhorrent and desperate though rather clumsy mode of fighting. Three of the _Emma's_ men, including Capt. Collins and First Mate Green, were killed; and the remaining eight under Second Mate Johansen proceeded to navigate the captured yacht, going ahead in their original direction to see if any reason for their ordering back had existed. The next day, it appears, they raised and landed on a small island, although none is known to exist in that part of the ocean; and six of the men somehow died ashore, though Johansen is queerly reticent about this part of his story and speaks only of their falling into a rock chasm.