In that year he was chosen treasurer of the Jackson Manufacturing Company, at Nashua, N. H., and began business as a manufacturer. Without experience, and yet with a mind which study had disciplined and knowledge of the world had made keen, with remarkable energy and enterprise, he was eminently successful, and the Jackson company paid large and sure dividends for the eleven years he continued its treasurer. In 1837 he became the treasurer of the Amoskeag Manufacturing Company, an office which included at that time, when the plan of creating a city upon the Merrimack was just to be carried out, the responsibility and wisdom of a general manager of the company's interests, as well as the usual financial duties of a treasurer. He held that office from then till October, 1876; was treasurer of the Stark Mills, with the exception of four years and a half, from its organization, in 1839, to 1876; was a director of the Manchester Mills, and its successor, the Manchester Print-Works, from the start, in 1839, till 1871; and has been a director of the Langdon Mills from its beginning, in 1860, and its president from 1874 to 1876. When Mr. Amory tendered his resignation as treasurer of the Amoskeag company, the following complimentary resolutions were unanimously adopted by the stockholders:-- "_Resolved_, That the stockholders of this corporation have heard with regret of the resignation of their treasurer, William Amory, Esq. "That a continuous service of thirty-nine years demands from them an expression of their appreciation of his eminent success, not only in building up an unequaled and remunerative manufacturing establishment, but in founding the largest and one of the finest cities in the state. "For both these results they tender to him their hearty thanks, and desire to place this testimonial upon the records of the company." In seconding the motion to adopt the above resolutions, T. Jefferson Coolidge, Esq., spoke as follows:-- "The best witness to the services of Mr. Amory as treasurer is the splendid condition of the Amoskeag company. He took it in its infancy, when it was poor. There was then but one mill of about eight thousand spindles. He leaves it, after forty years of success, with one hundred and thirty-seven thousand spindles, and more than two millions of quick capital. You have received in dividends, for forty-two years, an average of eleven per cent a year; and, if to that is added the increase of the quick capital, the company has earned fifteen per cent per annum, without taking into consideration the money spent on the plant. To put it in another light: a stockholder of one share, costing one thousand dollars, if he allowed compound interest at the rate he received on his dividends, would find that his share had been worth to him eighty thousand dollars.