The discovery, indeed, of the infamous wretches and their intended diabolical act is next to a miracle, and is only to be attributed to the determination and perseverance of the man who made the communication to the earl of Harrowby: he called at his lordship’s house, in Grosvenor-square, on Wednesday morning, (the 23d), between eleven and twelve o’clock, and inquired of the porter if the noble earl was at home? The porter replied in the negative. The man appeared very anxious to see his lordship, but the porter did not give him any hopes, as he refused to tell his business; the man, however, urged the necessity of seeing his lordship, without loss of time; and at length he observed, that if he did not see him, the porter would not be sitting in his chair in the hall to-morrow. This observation astonished the porter, and induced him to believe that the man really had something of a serious and alarming nature to communicate to the noble earl: he then told him that his lordship was riding on horseback in the park, directed him to that part in which he was most likely to find him, and described his groom and the livery he wore, _&c._ The man hastened to the Park, and discovered the groom, as described by the porter, hailed him, and asked him if the gentleman before was the earl of Harrowby? The groom replied in the affirmative. The man then told him, that he wanted and must speak with his lordship. The groom informed his noble master, who immediately stopped his horse. The man then presented a letter to him, which the earl opened and read. The man having informed him that he had a deal more to communicate, his lordship dismounted, and walked and talked with the man for some time; and the result of their interview was the communication to the secretary of state, of which we have just spoken. Precautions were immediately taken at the secretary of state’s office, for the discovery and apprehension of the villains. The first intimation that was given of the affair at the office in Bow-street was at past seven o’clock, when it was made known that a number of officers, constables, and patrol, would be wanted. Ellis, who is a conductor of a party of patrol, was ordered to leave his division, and repair to the office with the men under his direction. The expedition upon which they were to be sent was kept a secret till they started, which was between half-past eight o’clock and nine. The place of rendezvous of the assassins was in Cato-street, John-street, in the Edgware-road, where the neighbours had become alarmed by a number of strange men assembling in a stable, and a loft over it, after dark; sacks being hung up on the inside of the windows to prevent detection.