SUICIDE OF GEN. C. A. JOHNSON. WHILE SUFFERING FROM DISEASE HE SHOOTS HIMSELF. NEW-HAVEN, March 30.--Gen. Charles Adams Johnson, a descendent of John Quincy Adams, committed suicide at his residence, 76 Howe Street, to-day, by shooting. For the past week he had been afflicted with a skin disease, and it is believed that his mind was temporarily deranged by the illness. The fatal shot was fired at 7:so o'clock, just after he had spoken of going to New-York on business, and death resulted an hour later. Little is known in this city of Gen. Johnson's career. He and his wife came here five years ago. It is stated that the General was a native of Utica, N.Y., and that he belonged to a wealthy family in New-York City. A surviving brother resides at Newbury- port, Mass. Gen. Johnson was graduated from Yale Col- lege and adopted law as his profession. He acquitted himself with credit in the Mexican war. When the war of the rebellion broke out, he entered the service in the ranks, and before its close he was brevetted Brigadier General for bravery in the field. He entered the Army of the Po tomac, and on his promotion he was assigned to a Western command. He was a member of the Loyal Legion and was one of the most regular attendants at the dinners and receptions of that body in New-York. His age was about seventy years.