Photo Theodolite

Description:

Photogrammetry (surveying by photographic means) came into use in the middle years of the 19th century, especially in French, German and Italian lands. The Bridges-Lee photo-theodolite represents British work in the field. John Bridges-Lee (1867-1917), a scientist and lawyer in London, filed two British patent applications describing this instrument in 1894. He filed a third in 1896, and licenced Casella to bring it to the market. The Casella firm was still offering instruments of this sort in the 1930s. The U. S. Geological Survey transferred this example to the Smithsonian in 1909.The signature reads "BRIDGES-LEE’S PATENT PHOTO THEODOLITE L. Casella, LONDON No 8."

The instrument consists of a photographic camera with an internal compass card, housed in an aluminum box; there is a horizontal circle below, and a transit-mounted telescope with vertical arc above. The horizontal circle is graduated to 30 minutes, and read by vernier to single minutes. The vertical arc extends 90 degrees either way, and is graduated to 30 minutes and read by vernier and small telescope to single minutes. The whole instrument sits on a tribrach base, suitable for mounting on a tripod.

Ref: L. Casella, Description of the Bridges-Lee New Patent Photo-Theodolite (London, 2nd ed., 1899).

Anita McConnell, King of the Clinicals. The Life and Times of J. J. Hicks (1837-1916) (York, England, 1998), pp. 98-99. This discussion of the photo-theodolite is based in large part on the Bridges-Lee papers, Science Museum Library Archives, London.

"The Bridges-Lee Photo-Theodolite," Engineering (Sept. 10, 1897): 312, 314-315.

C. F. Casella & Co., Ltd., Catalogue No. 564. Surveying and Drawing Instruments and Appliances (London [about 1937]), pp. 35-36.

"Phototopography as Practiced in Italy under the Auspices of the Royal Military Geographical Institute, and as Practiced in the "Dominion of Canada under the Auspices of the Department of the Interior. Also a Short Historical Review of Other Photographic Surveys and Publications on the Subject," Report of the Superintendent of the U.S. Coast and Geodetic Survey for 1893 (Washington, D.C., 1895), Appendix 3.