BREAKDOWN ON THE UNDERGROUND RAILROAD - About sunrise yesterday morning, Mr. Joseph A. Chadwick, mate of the schooner Danyille, one of Currie & Bro.’s Richmond and New York packets, heard a strange noise proceeding, as he though, from the cook's galley, and knowing that the cook himself was absent at market, determined to ascertain the cause of the sound. He looked into the galley, but saw no one: he then lifted up the cook's mattress, which was lying on the chain box close by, and saw inside of the box a man's hand. Mr. C. immediately went and informed Captain Chester, who was conversing with the lock keeper, Mr. Nuckols, on shore, and the three went on board to investigate the matter. Mr. Nuckols lifted up the cover of the chain box, and found a negro named Tom, belonging to Mrs. James Grey, lying on a mattress in a very contracted space. Without farther search, they took Tom to the watchhouse. He had in his pocket $394 68, viz.: $263 in paper, $127 in gold, and sixty-eight cents in change, which he said he stole from his father-in-law; but this is believed to be a fabrication, as his father-in-law alleges that he has lost no money. Capt. Wilkinson, of the night watch, asked Tom if he knew anything of a negro belonging to Wm. H. Muciniland, Esq., named Martin, who ran away a day or two before. Tom at first denied any knowledge of him, but afterwards stated that if they would go and search the vessel they would find him. Accordingly, Capt. Wilkinson went down to the schooner, and getting Mr. Nuckols to aid him in the search, examined the chain box again. Lifting up the mattress upon which Tom had been laying, they discovered Martin underneath, nearly suffocated. From the fact that the cook, a New York negro, named Lot Munday, slept on top of the box, it was thought that he had furnished Tom and Martin with facilities of escape, and he was at once taken into custody. The Mayor's investigation of the affair elicited the facts we have given above. The two negroes, Tom and Martin, were then examined separately, and their statements very nearly agreed with each other: though the latter professed to have given up the whole management of the affair to Tom, who first proposed the scheme of escape. It appeared from their testimony, that they left their homes on Sunday night, and skulked about the suburbs until Tuesday night, when they went down to the dock, and saw Lot Munday, for the first time, sitting on the dock of the schooner Danville. Tom asked him if there was any chance to get off. Lot replied that he reckoned there was if they could keep still and make no fuss. Tom then agreed to give him $50 to aid them in escaping to New York, and he put them into the chain box. Both negroes said they were satisfied with their previous condition here, and had no expectation of living more at ease at the North. Tom declared that they merely wanted to go to New York for a frolic, and Martin said he had no thought of going, until his companion persuaded him into it. A letter, written by Mr. McFarland's niece, to a friend in New York, was found in Martin's possession. He had been directed to take it to the post office, but probably entertained the hope of delivering it in person. He had no money. Lot Munday was demanded to jail, to be tried before the Court of Hastings in August next. He has a white wife and two children in New York, though he is about the blackest negro we have ever seen. Tom and Martin were detained as witnesses. - Richmond Whig, July 24.