After Siebold’s return to Nagasaki, he continued diligently to follow out his object, keeping up, through means of the interpreters, a correspondence with his Yedo friends. In the course of five years he had not only made large collections for the government of specimens in natural history, but also, on his own account, of Japanese books and other curiosities, besides acquiring a considerable knowledge of the language. His collections in natural history had been shipped to Batavia; he was preparing himself to follow, when an unlucky disclosure took place. The imperial astronomer, notwithstanding the law to the contrary, had secretly sent him a copy of a new map of Japan, lately constructed on European principles. One of the draftsmen employed in making it having quarrelled with the astronomer, informed against him, in consequence of which the astronomer, his servants, the interpreters, several of Siebold’s pupils, and other Japanese suspected of being concerned in this affair, were arrested and subjected to a strict examination. Siebold himself was called upon to give up the map; and, when he hesitated about it, underwent a domiciliary visit, followed by an order to consider himself under arrest, and prohibition to leave Japan until the investigation was terminated. Finding thus not only the fruits of his own labor, but the lives of his Japanese friends in danger, he made a full confession as to the map, endeavoring thus to remove suspicions and to preserve some other documents in his possession, of which the Japanese yet had no knowledge, and which might have compromised other persons not yet suspected. Studiously concealing the connection of the Dutch government with his mission, he thought it best to represent himself as simply a private inquirer, whose researches into natural history and the physical sciences might be no less useful to the Japanese than they were interesting to himself. Of the particulars of this affair no account has ever been published. It is said that some of his Japanese friends found it necessary to cut themselves open, but Siebold himself was speedily released, with his entire collections, which he brought with him to Holland, and by means of which he converted his residence at Leyden into a very curious Japanese museum.