His naval and military experience naturally showed itself in Colonel O'Brien's general bearing; he possessed the polished manners and high-bred courtesy of some old Spanish hidalgo, together with a sufficient share of corresponding hauteur when displeased. The first whispers of the Rebellion of 1837, brought him to the front. He called together his loyal neighbours, who responded so promptly that not a single able-bodied man was left in the locality; only women and children, and two or three male invalids, staying behind. With his men he marched for Toronto; but, when at Bond Head, received orders from the Lieutenant-Governor to remain there, and take charge of the district, which had been the head quarters of disaffection. When quiet was restored, he returned to Shanty Bay, and resided there for several years; occupying the position of chairman of the Quarter Sessions for the Simcoe District. After the erection of the County of Simcoe into a municipality, he removed with his family to Toronto, where he entered into business as a land agent; was instrumental in forming a company to construct a railroad to Lake Huron _via_ Sarnia, of which he acted as secretary; afterwards organized and became manager of the Provincial Insurance Company, which position he occupied until 1857. In the year 1840, died Mr. Thos. Dalton, proprietor and editor of the _Toronto Patriot_ newspaper; the paper was continued by his widow until 1848, when Col. O'Brien, through my agency, became proprietor of that journal, which I engaged to manage for him. The editor was his brother, Dr. Lucius O'Brien, a highly educated and talented, but not popular, writer. Col. O'Brien's motive in purchasing the paper was solely patriotic, and he was anxiously desirous that its columns should be closed to everything that was not strictly--even quixotically--chivalrous. His sensitiveness on this score finally led to a difference of opinion between the brothers, which ended in Dr. O'Brien's retirement.