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
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