The authorities of CUBA have decided to release the American prisoners taken from the island of Contoy, beyond Spanish jurisdiction. This will probably terminate all difficulties between the two governments growing out of this affair.--Considerable currency has been given to a story stated by correspondents of the London press, that the Spanish Gen. NARVAEZ had grossly insulted the U.S. Minister at Madrid, refusing in public to hold any intercourse with the representative of a nation which tolerated and countenanced pirates and assassins. The story is entirely discredited by direct advices.--The State Convention of Ohio called to revise the Constitution has adjourned until the first Monday in September.--A very destructive fire occurred at Philadelphia on the night of the 9th ult. Although not in the chief business part of the city, property to the amount of more than a million of dollars was destroyed, and over _thirty_ lives were lost by the explosion of various materials in the buildings burned The occurrence has elicited from Prof. ROGERS, of the University of Pennsylvania, a letter stating that, in his opinion, saltpetre by itself is not explosive, but that the great quantity of oxygen which it contains greatly increases the combustion of ignited matter with which it may be brought in contact, and that this may evolve gases so rapidly as to cause an explosion.--The cholera is prevailing with a good deal of fatality in some of the western cities. In Cincinnati the number of deaths has averaged 20 to 35, and has been as high as 65: in St. Louis it has been still higher, and in Nashville, Tenn., it has been quite as large in proportion to the population. At the latest advices it seemed to be diminishing. It has not made its appearance in any of the eastern cities.--The case of Prof. WEBSTER, convicted at Boston of the murder of Dr. PARKMAN, has been definitively decided. Soon after the trial he sent in a petition for a full pardon, on the ground of his entire innocence and ignorance of the whole matter, solemnly asserting, and calling God to witness, that he knew nothing whatever of the manner in which Dr. Parkman's remains came to be found in his room. A few days afterward he sent in another petition, praying for a commutation of his sentence. It was presented by the Rev. Dr. PUTNAM, who had acted as his spiritual adviser, and who laid before the Council a detailed confession, which he had received from Prof. Webster, in which he confessed that he killed Dr. Parkman with a single blow from a stick, but claimed that it was done without premeditation, in a moment of great excitement caused by abusive language. He gave at length a statement of the whole transaction. After considering the subject fully and carefully, acting under the advice of the Council, Governor Briggs decided against the application, and appointed Friday, the 30th day of August, for the execution of the sentence of the Court. Upon that day, therefore, Prof.