As to the nature of the explosive and of the deflagrator, the elements of which the latter was composed, their manufacture, and the way in which they were employed, he preserved complete silence, and all attempts to worm the secret out of him remained ineffectual. Once or twice, during the height of the paroxysms to which he was occasionally subject, there had been reason to believe that his secret would escape him, and every precaution had been taken to note his slightest utterance. But Thomas Roch had each time disappointed his watchers. If he no longer preserved the sentiment of self-preservation, he at least knew how to preserve the secret of his discovery.

Pavilion No. 17 was situated in the middle of a garden that was surrounded by hedges, and here Roch was accustomed to take exercise under the surveillance of his guardian. This guardian lived in the same pavilion, slept in the same room with him, and kept constant watch upon him, never leaving him for an hour. He hung upon the lightest words uttered by the patient in the course of his hallucinations, which generally occurred in the intermediary state between sleeping and waking--watched and listened while he dreamed.

This guardian was known as Gaydon. Shortly after the sequestration of Thomas Roch, having learned that an attendant speaking French fluently was wanted, he had applied at Healthful House for the place, and had been engaged to look after the new inmate.

In reality the alleged Gaydon was a French engineer named Simon Hart, who for several years past had been connected with a manufactory of chemical products in New Jersey. Simon Hart was forty years of age. His high forehead was furrowed with the wrinkle that denoted the thinker, and his resolute bearing denoted energy combined with tenacity. Extremely well versed in the various questions relating to the perfecting of modern armaments, Hart knew everything that had been invented in the shape of explosives, of which there were over eleven hundred at that time, and was fully able to appreciate such a man as Thomas Roch. He firmly believed in the power of the latter's fulgurator, and had no doubt whatever that the inventor had conceived an engine that was capable of revolutionizing the condition of both offensive and defensive warfare on land and sea. He was aware that the demon of insanity had respected the man of science, and that in Roch's partially diseased brain the flame of genius still burned brightly. Then it occurred to him that if, during Roch's crises, his secret was revealed, this invention of a Frenchman would be seized upon by some other country to the detriment of France. Impelled by a spirit of patriotism, he made up his mind to offer himself as Thomas Roch's guardian, by passing himself off as an American thoroughly conversant with the French language, in order that if the inventor did at any time disclose his secret, France alone should benefit thereby. On pretext of returning to Europe, he resigned his position at the New Jersey manufactory, and changed his name so that none should know what had become of him.

Thus it came to pass that Simon Hart, alias Gaydon, had been an attendant at Healthful House for fifteen months. It required no little courage on the part of a man of his position and education to perform the menial and exacting duties of an insane man's attendant; but, as has been before remarked, he was actuated by a spirit of the purest and noblest patriotism. The idea of depriving Roch of the legitimate benefits due to the inventor, if he succeeded in learning his secret, never for an instant entered his mind.

He had kept the patient under the closest possible observation for fifteen months yet had not been able to learn anything from him, or worm out of him a single reply to his questions that was of the slightest value. But he had become more convinced than ever of the importance of Thomas Roch's discovery, and was extremely apprehensive lest the partial madness of the inventor should become general, or lest he should die during one of his paroxysms and carry his secret with him to the grave.