No. 1 6.0 seconds. 6.31 × 5 = 31.55 2 6.0 seconds. + 1.00 3 6.7 seconds. ---- 4 6.3 seconds. 5 6.5 seconds. 32.55 6 6.7 seconds. 32.55 ÷ 6.31 = 5.159 7 6.0 seconds. With fork free 5.163 ---- ----- Mean = 6.31 seconds Effect of scrape = - .044 _Specimen._ Circumstances as in first case, except that both forks were on their resonators. Coincidences were observed at-- 21 seconds. 28 seconds. 36 seconds. 44 seconds. 51 seconds. 60 seconds. 60 - 21 = 39 39 ÷ 5 = 7.8 = time of one interval. _Résumé_. No. 1 7.8 seconds. 7.42 × 5 = 37.10 2 7.1 seconds. + 1.00 3 7.6 seconds. ----- 4 7.4 seconds. 38.10 5 7.2 seconds. 38.10 ÷ 7.42 = 5.133 ---- (Above) 5.159 ----- Mean = 7.42 seconds. Effect of support and scrape = - .026 Mean of second determination was 256.094 Applying correction (scrape, etc.) - .026 ------- Corrected mean 256.068 Result of first determination 256.072 ------- Final value 256.070 NOTE--The result of first determination excludes all work except the series commencing July 4. If previous work is included, and also the result first obtained by Professor Mayer, the result would be 256.089. 256.180 256.036 256.072 256.068 ------- Mean = 256.089 The previous work was omitted on account of various inaccuracies and want of practice, which made the separate results differ widely from each other. The Formulæ. The formulæ employed are-- d′ (1) tan φ = ----- r 2592000″ × D × n (2) V = ----------------- φ″