60 
LL. Waldo—Papers on Thermometry. 
has its connection at the level of the thermometer bulbs, and a 
small thermometer is inserted at the top of the steam chamber 
to assure the observer that the temperature at the top is at 
100° C. The escape of the steam is t 
roug 
a small vent at 
.the top of the tube, and the amount of its opening is controlled 
by a small brass plate. 
The details of the calibration of the Kew thermometers have 
ratus IJ, and special care was taken to 
changes of temperature. 
he reduced resul 
uar 
ts are as follows, 
where each line is the mean of three observations :— 
Computed 
maher | Date, |Extreme readings. tength Fh. guapouoe bron: Remarks. 
~ | 1880 e z . ‘ 
Kew 578/Oct. 15} —1°l +383°6} 32°487 |At32°C. = +0°007| The observations were all 
+31°0 +6571) 32°507 65°C. = —0-014|made by daylight and at one 
+63°T +98°6| 32°487 99°C. = + 0°007|sitting for each thermometer. 
The extreme variations of 
Kew 584/Oct. 15} +32°2 +82°3| 49°040 9°F. = +0°021/|the temperature of the roo 
+761 +1273) 49°068 | 123°F, = —0-006/during the observations, a8 
+119°1 +170°1| 49°078 | 166°F. — —0-016|measured by two thermom- 
41622 +2132) 49:060 | 212°F. = +0-001\eters, one at each end of the 
tube being measured, was 4 
Kew 585/Oct. 15 49813 0°C. = +0°015/follows: 
+49°0 +100°9) 49°843 100°C. == + 0:0 sail 
+99°1 +151°7| 49°820 | 150°C. = +0-008| Kew 578 = iy 4 
+148°9 +201°0| 49-807 150°C. = +0°029 585 ERE 01 
4+199°2 +250°8| 49-747 250°C. = +0°110 we 
The length of the column 
by which the thermometers were graduated, was 5 
Kew 578, 10°-405 for 584, and 10°-673 for Kew 585. 
may, therefore, conclude that between 0° and 100° C. 
used for the Kew calibration, and 
026 C. for 
° 
e 
errors of the three Kew standards, depending on the calibra- 
tion, are practically insensible; for the errors shown above are 
too small to be certainly detected, owing to the width and 
irregularity of the 
thermometer scales 
lines which make up the graduation of the 
Accidental errors of graduation could not be guarded against 
except by the direct examination of every degree, and that 
accordingly has been done. 
The tedious examination of each degree was accomplished 
with the 
aid of P 
rofessor J. E. 
. 
ershner, now of the Franklin 
and Marshall College, but who was until recently connected with 
the observatory. We used the apparatus I, and each degree 
