MAURICE LANGHORN, one of the principal government witnesses, was born in Pittsburgh, Penn., and reared in Marysville, Ky. He is a lawyer, and a man of ability. Like many other Kentuckians who were in the South at the time the rebellion broke out, Mr. Langhorn committed himself to the doctrine of secession. In 1861 he enlisted as a private in a Louisiana regiment of heavy artillery. He was subsequently recommended for Colonelcy in the rebel army, but failed to get the appointment. In 1861 he went to Bowling Green, Ky., where he enlisted as a private in the 9th Kentucky Infantry, Col. Thomas H. Hunt, of Louisville, and was transferred to the artillery. He mounted the guns on the fortifications around Bowling Green, and seems to have given great satisfaction. He ran as candidate for representative to the rebel congress from Kentucky, but before the result of the canvass was known, was captured and held eight months as a prisoner of war. Mr. Langhorn subsequently took the oath of allegiance to the United States, and was of great service in reporting the movements and designs of the rebel emissaries in Canada to Col. Sweet. The information Mr. Langhorn gave of those men was reliable, and upon it certain arrests were made. Mr. Langhorn is now a loyal citizen, in its broadest and best sense. Mr. Langhorn is a young man not over twenty-five years of age, of quick, nervous temperament, kind and generous impulses, a man of strong feelings, warm friendship, bitter animosities, and whatever he undertakes, he executes with a will. Of Mr. Langhorn it may be truly said, that while he was a rebel, he was an earnest, active foe, but a true soldier, having a high regard for honor and integrity, loving the State in which he was reared, and ever jealous of her honor and fair name. Mr. Langhorn was a rebel from principle--because he felt that the South was right--but when convinced of his error, he made haste to repair it, and when he had once taken the oath of allegiance, he went to work with all his might to aid the cause of the Union. To Mr. Langhorn is due all the honor of frustrating the designs of the _rebels from Canada_; and Col. Sweet being advised by Mr. Langhorn of _this_ portion of the plot, and by the writer of the _Copperheads' movements and intents_, the Colonel had the best possible opportunity of acquiring important knowledge, and regulating his conduct in accordance therewith. Mr. Langhorn is a true friend of the Union, an admirer of our lamented President, and has rendered the citizens of Chicago a service which should ever be held in grateful remembrance.