3U 



27 — 23 = 0.^84. 



llcductltni hl/ inedii^ of I^. Fiom several sei-ies of observalioiis at 

 a mean temperature of 16°.44, Tresca found (Vol. Ill, p. 14) 



23 = 7, + 1^24. 

 Adding 0^02 X 16.44 = ().".33 for the reduction to 0° the ecpiation 

 becomes 



23 = /, -f 1^57, 

 fiirlher 27 — 23 + 0.«.84 (see above) 



and /, = J/+ 5.-.94 (Vol. Ill, p. 70), 



so thai 27 = 37 4-8^35. 



Reduction hij nimns of 20. From three series of measurements 

 one by Hosscha and two by Tkesca, follows : 



23 = 20 + 7.".19 (Vol. Ill, p. 24), 

 further 27 = 23 + 0^84 (see above) 



and 20 = J/ +0^.96 (Vol. Ill, p. 70), 



so that 27 = J/ +8^99. 



The mean of the two reductions is 27 = i/ -|- 8.".67. 



If the 5 above mentioned ditferent equations containing 4 unknown 

 (puintities, are taken as all equally accurate and if they are then 

 solved by the method of least squares, obviously the same value 

 for 27 — M is found, while the mean error of each of the equations 

 is ±0.^32, that of 27 — J/=8^67 being ±0-^45. 



A value for 27 — 31 is also arrived at by using the comparisons 

 with the "Metre des Archives" A, viz. 



27 = .4 + 6/^11 (Vol. II, p. 323), 

 ^=.l/+2.-.63 (Vol. Ill, p. 24, 70„ 

 Hence 27 = J/+ 8.".74. 



This result agrees very closely with the value found above. But, 

 as it is largely based on the comparisons which have also served 

 for calculating the previous result, no particular importance can be 

 attached to the accordance. Considering the value of the mean 

 error ± 0'".45 a direct comparison of 27 and 31 would certainly 

 seem to be desirable. 



If the length of the measuring bar of the French base-apparatus 

 in terms of metre 27, as given in the previous note, is now expres- 

 sed in International metres by means of the equation 27 = M -\- 8^.67 

 the result is; 



