Tape contact at middle of comparator

Tape contact at middle of comparator. Basically calibrating steel tapes - first use of steel measuring tapes by C&GS. Nine bases being measured on 98th Meridian by base line party under A.L. Baldwin . Fig. No. 15, Appendix No. 3, Report of Superintendent ... 1901, p. 260. Work done at night to reduce expansion and contraction of steel tape

Photo Category: Geodesy - Base Line
Photo Date: 1901