Cambridge, Massachusetts: American Social Science Association 1870. First Edition. ,[1-blank], -19, [3-blank] pages plus blue printed wrappers. 8vo. Dampstaining, sunning to wrappers. The inside front and rear wrappers note contents of the Association's Journal for 1869 and 1870, the rear cover a description of the Association and it's goals. Good. Pamphlet. 
"Samuel Augustus Duncan enlisted as major in the 14th New Hampshire Infantry Regiment in Sept. 1862. In Sept 1863 President Lincoln commissioned Duncan, who was white, as colonel of the 4th U.S. Colored Troops Infantry Regiment." He was wounded at New Market Heights and breveted Brigadier General. ("Yankee Correspondence: Civil War Letters Between New England Soldiers and the Home Front", Associate Professor of History Nina Silber, Univ of Virginia Press, 1996, p. 51)
Duncan provides some background on patent law in America (starting in 1790), and does a nice job of arguing why patent protections are valuable, the role of the Patent Office, and some practical sense of the volume of work and patents issued by 1870. At times he contrasts the American system with other international systems. He also records and rebuffs typical detractor complaints about the system, but clearly comes down on the side of patents being a useful and essential part of American entrepreneurship. The talk was given to the American Social Science Assocation, organized only five years before, in 1865 "after the model of the British Association for the Promotion of Social Science." At this time the Presidentof the Association was Samuel Eliot and the Secretary was Henry Villard.
A surprisingly scarce pamphlet, with one physical copy in OCLC (Acc #: 69007037) in the Netherlands, and two Harvard locations with a microform copy (Acc# 26080363) noting different pagination and it's appearance in the Journal of social science, 1871.