Dr. Clark continued in the practice of medicine for a quarter of a century after the formation of the Moreau temperance society, making his residence on the farm of his original purchase. Of this long period of professional labor there remains no memorial, though in common with the routine duties of medical men, it undoubtedly abounded in elements which, interesting of themselves, would be all the more so as belonging to the life of one so distinguished in the annals of reform. Beginning to experience the physical effects of his protracted devotion to his profession, and having accumulated considerable property, Dr. Clark in 1833 purchased real estate in Glens Falls and embarked there in the retail drug business. This successful enterprise engaged his attention until 1849, when he retired from trade. Two years later, longing for the quiet life on the farm, he returned to reside at the old home at Clark's Corners. He was now at the age of seventy-three, but enjoyed, with the exception of a gradual failing of the sense of sight, an almost unimpaired mental and physical vitality. But the gloom before his eyes grew remorselessly thicker and thicker until every familiar scene and the faces of family and friends faded from his view. In the custody of this great affliction, the spirit of Dr. dark was not crushed, but rather purified and exalted, so that he who in earlier years had been conspicuous as the heroic leader, was now none the less remarkable for his Christian humility, hope and love. A few years longer he tarried upon the earth, in order that there might be registered upon the hearts of men the beauty and nobility of the character that was his. And then, at Glens Falls, in the home of his son, James C. Clark, the spirit of the great reformer went to its long home. His death occurred on Wednesday morning, September 20, 1866. Dr. Holden says: "The intelligence of his departure was swiftly borne through the place; his name was on every lip as all, with hushed reverence, bore testimony to his virtues, and to the usefulness of a life luminous with the light of a Christ-born principle." Notwithstanding his portrait, in its severe lines, gives evidence of his decisive mind and undeviating purpose, he yet possessed elements of character that endeared him to all. While in terms of affectionate banter, alluding to his spirit of determination and his practice of proposing to formulate the mind of public meetings in resolutions, he was sometimes spoken of as "Resolution Billy," the people knew that beneath the crust of self-reliant earnestness dwelt the loving humanitarian and the undying fires of a moral volcano.