of Edinburgh, Session 1871 - 72 . 599 
Hence 
SE = J (oll-tSj) = J^ot . 
Introducing the hypothesis, obtained from considerations of Dissi- 
pation of Energy, (Proc. Dec. 19, 1870) that 
= Kt, <r s = k b t i 
we have 
J T = S = ( ^-^ 
where T ab is the well-known “ neutral point.” 
Also 
e ={K-h)(f-h) ( t *-^), 
since it vanishes for t = t v the temperature of the cold junction. 
Now, if the neutral point be between such limits as 0° 0. and 300° 
C., the exact determination of it is an easy matter; and this ex- 
cZE 
act knowledge of it greatly facilitates the determination of 
which cannot be very accurately found by drawing a tangent to the 
plotted curve. For if one junction be at t , the other at T a6 , we 
have 
= ~ “ 0** 
E t and T ab - 1 are easily measured on the experimental curve, and 
thus h a -h b is found. The following values have thus been 
(roughly) calculated from observations. Where the neutral point 
was not reached, it is put in brackets. The unit for h a - Jc h is 3 or 4 
2 
'per cent, less than — of the electromotive force of a good G-rove’s 
cell. 
Fe-Cu (had) 
T 
265 C. 
Tc a ~ Jcb 
-0-00147 
Fe-Al 
T 
(387) C. 
k 
'a — tcb 
0-00105 
- Cu (good) 
260 
- -00145 
>» ~ Arg. 
Cu (bad) - Cd 
(1357) 
- 
•00045 
„ -Cd 
159 
- -00209 
-(23) 
- 
•00081 
„ -Zn 
199 
- -00189 
„ -Zn 
-(146) 
- 
•00048 
„ -Ag 
235 
- -00151 
» - Ag 
- (687) 
- 
•00006 
„ -Pb 
(357) 
- -00112 
, , (good) - Pb 
-(213) 
+ 
•00016 
,, - Brass 
(318) 
- -00127 
Pb-Cd 
-(74) 
- 
•00096 
„ -Pt 
(519) 
- -00063 
„ - Pd 
-(188) 
+ 
•00080 
„ -Sn 
(416) 
- -00094 
,, - Zn 
-(78) 
- 
•00060 
,, - Pd 
(1908) 
- *00029 
„ - Ag 
- (262) 
- 
•00026 
