26 
PROFESSORS W. E. AYRTOY AYD J. PERRY 
that must have been introduced by former experimenters using a moist blotting paper 
surface instead of the surface of a liquid itself. (See page 15, “Reasons for Incom¬ 
pleteness of Early Experimenters.”) 
Date. 
The following — 
Has to the following — 
At — 
A. contact 
difference 
of 
potentials, 
in volts. 
Remarks, 
12/4/78 . 
Mercury. 
Mercurous sulphate 
° c. 
15 
-0-092 
Connexion between the mercury and the 
23/4/78 . 
paste 
17 
+ 0'4Q5 
paste made by a small glass siphon tube 
filled with the paste. Connexion with the 
„ . 
17 
+ 0-420 
earth made by a platinum wire dipping 
24/4/78 . 
79 . 
10 
+ 0-360 
in the paste in the last four, and with 
25/4/78 . 
r . 
97 97 
17 
+ 0-470 
an iron wire dipping into the mercury 
13/4/78 . 
Saturated solution 
16 
+ 0-103 
in the first case. 
Connexion between the liquid and the 
zinc sulphate 
99 99 
17 
+ 0-106 
paste formed by a tube filled with the 
paste, but neither were connected with 
the earth. 
Zinc sulphate solution connected with the 
23/4/78 . 
18 
+ 0-740 
earth by a platinum wire, the connexion 
with the paste remaining as before. 
97 91 19 
24/4/78 . 
,, „ 
18 
+ 0-900 
99 99 I' 
18 
+ 0-720 
27/4/78 . 
, , , 
19 
+ 0-100 
Connexion between the liquid and the 
91 17 
19 
+ 0-080 
paste formed by a very clean cotton 
,, 
99 ' 9 
19 
+ 0-120 
wick previously soaked in the saturated 
9i 97 
19 
+ 0-090 
solution of pure zinc sulphate. Con¬ 
nexion with the earth made by a plati¬ 
num wire dipping into the porcelain 
vessels containing the zinc sulphate. 
In order to ascertain whether the high or the low value for the constant difference 
of potentials of zinc sulphate with mercurous sulphate was correct, an incomplete cell 
of zinc sulphate solution, mercurous sulphate paste, and mercury was formed, and the 
electro-motive force measured, the arrangement employed consisting of the zinc sulphate 
solution being put in one of the porcelain dishes, and in the other the mercury, 
the two being connected with a small beaker containing mercurous sulphate paste, 
and which did not act inductively on the induction plates. The connexion between 
the zinc sulphate and the mercurous sulphate was made by a clean cotton wick 
previously soaked in a saturated solution of the former, and the connexion between 
the mercury and the paste in the beaker by a small glass siphon tube filled with the 
latter. Earth connexion in the first experiment recorded was made by a platinum 
wire dipping into the mercury, afterwards by a platinum wire dipping into the zinc 
sulphate instead of into the mercury. 
Saturated zinc sulphate and mercury connected by mercurous sulphate paste. 
Date. 
24/4/78 
25/4/78 
27/4/78 
Temperature. 
17° 
O 
Difference of potentials in volts. 
-b 0-725 
— 0-330 
•f- 0 '7 / 0 
19' 
