bam/8.] CALIBRATION OF ELECTRICAL PYROMETERS. 
Table 9. — Comparison of standard elements. 
[All values reduced to 20° C] 
101 
Standard Daniell cells. 
Date. 
Latimer- Clark standards. 
Siphon-joined cells. 
Sepa- 
rate 
cells. 
Beetz {xypsuin 
cells. 
Tem- 
pera- 
ture. 
D. 
E. 
F. 
Elliott, 
114. 
Elliott, 
115. 
G. 
H. 
I. 
Q- 
9- 
h. 
i. 
Dec. 18, 1883.. 
1.420 
1.420 
1.420 
1.420 
1. 420 
1.420 
1.420 
1.426 
1.427 
1.428 
1.420 
1.420 
1.426 
1.426 
1.430 
(1.056) 
1.050 
(*) 
U4° 
Jan. 2, 1884 . . 
1.384 
1.371 
1.350 
1. 403 
1.050 
1.052 
Oct. 26 1885 
1.083 
1. 022 
1.030 
1.083 
1. 037 
1.024 
1.081 
1.013 
+19° 
§20° 
28° 
Mar. 22, 1886 
1.306 
1.076 
1. 079 
1.074 
1.075 
Aug. 13, 1887. 


* Immediately after making the Latimer-Clark elements D, E, F. 
t Immediately after making the Daniell G, IT, I. 
t Immediately after receiving the Elliott standards. 
§ Immediately after making the Daniell Q. 
In the construction of this table the element D is assumed to be con- 
stant, aud with this premise the data of the table are at once intelligi- 
ble. I need only remark that my Latimer-Clark standards, as compared 
with the separate-celled Daniell Q during the seventeen months of ob- 
servation, are as good as absolutely constant. It is for this reason that 
I am warranted in placing much confidence in the data of both these 
couples, of which the Daniell has the advantage of constancy and the 
disadvantage of less facile manipulation. The siphon Daniells are in- 
ferior to the form Q, as are also the Beetz patterns, concerning which, 
however, it is necessary to remark that the gypsum mixture of copper 
sulphate and zinc sulphate solutions were probably too moist. I found 
after a time that the line of demarkation had disappeared and that the 
solutions must have diffused into each other. 
It will be seen that the elements D, E, F, though identical among 
themselves, differ considerably from Elliott's Latimer-Clark's; not more 
so, however, than Elliott's elements differ among themselves. A much 
more curious result was obtained in measuring the temperature coeffi- 
cients of the siphon Daniell's and the Latimer Clarke's. To do this 
the elements were first covered with melting snow and afterwards sub- 
merged in water heated to different temperatures. Measurements were 
made by the zero method described, and to give additional certainty an 
auxiliary Daniell was used for comparison. In other words, the ele- 
ments g, h, i, E, F, heated to the temperature specified, were compared 
with D and B kept cold, by inserting them alternately in the same con- 
nections ; I) was compared b'y a galvanometer method. The main com- 
parisons were made in 1883, certain corroborative data added in 1887. 
a is a mean constant, derived graphically and intended for practical 
reductions only. Electromotive forces are given in volts. 
(755) 
