( 208 ) 
between the upper and lower thermometer for this period after the clock 
had been mounted in the niche. The monthly means of these differences, 
resulting from the five hours of observation and from the three years 
1899—1901, are as follows: 
January —+ 0.02 July > 0.21 
February + 0.01 August + 0.17 
March + 0.01 September + 0.06 
April + 0.02 October + 0.02 
May + 0.05 November + 0.01 
June + 0.15 December + 0.02 
The differences are now expressed in degrees Celsius. The index- 
errars of these thermometers are insensible. 
18. The observed daily rates were originally reduced to 760 Mm. 
and + 10°C. by means of the coefficients : 
b= + 05.0140 
In the following table, however, the Red. D. R. I. have been 
computed, not with this value of the temperature coefficient, which 
had originally been derived from only the first months, but with the 
value 
C= 00220 
which accords better with the observations. The meaning of the 
two last columns of the table will be explained hereafter. 
The four months immediately following the mounting and the 
regulation of the clock, during which the rate proved to be still some- 
what variable, have been left out of consideration and have not 
been inserted in the table. 
| Obst | NE | foe: ‘| Redd Reda | Reda 
AE: | DRI | DRT DR 
| _ 0157 | —0'169 
1899 May 0146 | 7632 | 4044.8 | — 040 en 2) eee 
June 0.132 | 65.7 15.0 0.402 | 4-647 ee 
July 0.192 | 65.4 18.4 0,090 | +45 A2 AE 
Aug Je beau dee Dek A87 0.490 EE VET An 
Sept. 0.353 | 59.4 16.0 0508 is ae 
