This transit was made in 1877 for the new John C. Green Astronomical Observatory at
Princeton University, and resembles the instruments that Stackpole & Brother had made for the
1874 transit of Venus. It has a "broken" telescope that is viewed through one end of the
horizontal axis, a micrometer eyepiece, a cast iron base, and a mechanism that is used to lift and
reverse the telescope. The vertical circle is silvered, graduated to 10 minutes, and read by
opposite verniers to 10 seconds. Edward Kahler (1832-1890) was born in Germany, and is listed
in Washington, D.C. directories from 1869. Charles A. Young, the newly appointed astronomer
at Princeton, carried on a lengthy correspondence with Kahler, repeatedly modifying the design
even as the instrument was being built.
Ref: Charles A. Young papers, Princeton University Archives.
