370 
Proceedings of the Boyal Society 
In Case II. the same bar was employed in a similar way, except 
that the surface was covered with paper, by which the superficial 
radiation was greatly increased. 
In Case III. an iron bar, one inch square, was used. The iron 
was from a different manufactory. The surface was moderately 
polished. 
The two first cases correspond to those worked out in the former 
paper. (“ Transactions,” vol. xxiii. p. 145. “ Proceedings,” vol. iv. 
p. 609.) The results obtained in the present paper, after all cor- 
rections are applied, differ hut slightly from those previously 
given. The conductivities deduced from the two first cases coincide 
with one another remarkably well, although the data are perfectly 
distinct. In Case III., that of the thin bar, the numerical values 
of the conductivity are considerably smaller than in the former 
instances, which is attributed to the different quality of the iron. 
In all the cases the conductivity diminishes as the temperature in- 
creases, and diminishes more rapidly in the lower part of the scale 
of temperature. The following numbers will be found (for Cases I. 
and II.) to be nearly identical at 0° and 150° with those previously 
published from less accurate data : — 
Conductivity of Wrought Iron. 
Temperature, 
Units, the Foot, Minute, and 
Units, the Centimetre, Minute, 
Centigrade. 
Cent. Degree. 
and Cent. Degree. 
Cases I. and II. 
Case III. 
Cases I. and II. 
Case III. 
0° 
•01337 
•00992 
12-42 
9-21 
50 
•01144 
•00904 
10-63 
8-37 
100 
•01012 
•00835 
. 9-40 
7-76 
150 
•00934 
•00795 
8-68 
7-38 
200 
•00876 
•00764 
8-14 
7-10 
250 
•00826 
•00736 
7-67 
6-84 
2. On the Chemical Composition of the Waters of the 
Beauly, Inverness, and Moray Firths. By Dr Stevenson 
Macadam. 
These three firths denote different parts of an arm of the sea 
which has two constrictions ; — one between Craigton Point and 
Longman Point, and the other between Fort George and the 
