Rittenhouse made other telescopes which survive, notably two zenith sectors now in the U.S. National Museum of the Smithsonian Institution,[2] but he does not appear to have made them for commercial sale. In the history of telescope-making in America he seems to have been something of a “sport.” Not only were the instruments which still grace the desks of Washington, Jefferson, and others, of European manufacture, but the earliest observatories in the United States (eleven between 1786 and 1840) were outfitted exclusively (except for the Rittenhouse observatory) with European instruments.[3] In its endeavor to establish a permanent observatory even Rittenhouse’s own Philosophical Society seems to have thought exclusively in terms of instruments of European manufacture. It must therefore have required some courage for Amasa Holcomb, 43-year-old Massachusetts surveyor, to approach Professor Silliman of Yale in 1830 with a telescope of his own construction. In the autobiography printed here, Holcomb states that all the telescopes used in this country before 1833 had been obtained in Europe, and indicates that thereafter “the whole market was in his hands during thirteen years,” a period which would fall, apparently, between 1833 and 1845. It should be mentioned, although it is no conclusive negation of Holcomb’s claim, that the New York instrument-maker Richard Patten in 1830 built a telescopic theodolite that was designed by Ferdinand Hassler for use on the Wilkes Expedition, and was subsequently used at the observatory of the Navy’s “Depot of Charts and Instruments” in Washington.[4] We do not know the source of Patten’s lenses. Holcomb would appear to have succeeded as a commercial maker of telescopes. He claims to have sold his instruments “in almost every state in the Union,” and also abroad, but we know nothing of what use was made of any of them. The telescope he showed Professor Silliman was a refractor. Another, preserved in the Smithsonian Institution,[5] is like Rittenhouse’s 1769 instrument, a transit. But Holcomb seems to have specialized in reflectors of the Herschelean type, _i.e._, instruments, in which the image is viewed through an eye-piece located at the mouth of the tube. It is probably reasonable to doubt that the serious astronomer of this period shared Holcomb’s enthusiasm for this type of difficult-to-adjust instrument in the small sizes he produced (10-inches is the largest reported). In 1834, 1835, and 1836 he presented instruments of this type to the Franklin Institute in Philadelphia, where committees compared them with the best available European refractors and found them more than adequate. One of Holcomb’s instruments of 1835, apparently his only surviving reflector, is now in the Smithsonian Institution (see appendix, p. 184).