This transit was made in the early 1850s. The horizontal circle is silvered, graduated to 20 minutes of arc, and read by opposite verniers to 30 seconds. The vertical circle, which was probably silvered, is graduated to 30 minutes of arc, and read by vernier to single minutes. The inscription reads "Stackpole & Brother New York 119"
William Stackpole (1819–1895) and Robert Stackpole (1823–1873) were Irish immigrants who arrived in the United States in 1833. Trading as Stackpole & Brother, they began making mathematical instruments in 1851. During the Civil War, they made spyglasses and sextants for the Navy. Each Stackpole instrument carries a serial number, and the sale of instrument #655 in 1866 suggests that the firm averaged some 44 instruments per year. According to the 1870 Census of Industry, the Stackpoles had $12,000 invested in the firm, hired eleven men and two children, and were then producing 250 surveying and nautical instruments worth $26,900. In the early 1870s they made instruments for the American expeditions sent to observe the transit of Venus. The firm remained in business until 1910.
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