ke 
(oa) 
found that the pivots were more or less affected, and on the suspen- 
sion-spring there was a small stain of rust, which had fortunately 
not eaten into the metal. 
Further rather large deviations are shown by the reduced rates, 
whenever the temperature was below O°. This is clearly shown 
by the monthly means for 1890 December and 1891 January, during 
which months the temperature was almost constantly below zero. 
It might be thought that this points to the existence of a term depend- 
ing on the square of the deviation of the temperature from its mean 
value. Such a term might be explained by an influence of the 
temperature on the elasticity of the suspension-spring. ') 
It appeared however, as will more amply be shown below, that 
the monthly means show little evidence of the influence of a qua- 
dratie term, so long as the temperature remains above zero. It 
would seem that the temperature-coefficient changes more or less 
abruptly near O°, its value for lower temperatures being much larger. 
I have therefore excluded all periods during which the tempera- 
ture was below O° (or rather below — 0.°6 R.) Four months, viz: 
1879 Dec, 90 Dec, 91 Jan. and 93 Jan. must consequently be exclud- 
ed entirely. In 16 other months the temperature was below zero on 
104 days. For these months new means were formed, excluding 
those days. ® The following table gives the altered reduced mean 
daily rates, together with the corresponding mean temperatures. 
Redd: 
Redd | 
Temp. DRI 
Temp. | Heed 
5 s 
1880 January .| + 2.4 | + 0.133 1891 December} + 5.4 + 0,208 
| 
1881 January.) + 2.3 | „199 1892 January ., + 3.4 „195 
1885 January.) + 2.5 161 » March. | +39 | „239 
1886 Decéthher | + 4.2 161 » December; + 4.6 190 
1887 January. +--1.5 | „205 1894 January .| + 3.2 „216 
1888 January .| + 2.9 | 263 » February | -+ 4.9 „232 
» February! — 2.7 „264 1895 January.) + 2.3 „174 
1889 February | -+ 3.4 | 268 » February) +422 | 146 
1) Investigations by Dr. P. J. Karser about the clock Honwi 27, belonging to 
the Bureau of Verification of the Nautical instruments belonging to the Dutch navy, 
have shown that the nature of the suspension-spring has a considerable influence 
on the value of the temperature-coefficient. 
2) Since there were not always time-determinations exactly at the beginning 
and the end of each cold period, some more days had to he excluded. 
6: 
