593 
of Edinburgh^ Session 1865-66. 
importance in the deeper speculations of natural philosophy, but of 
very great practical value. Other experimenters had given tolerable 
approximations to the relative conductivities of different metals, but 
had either not attempted, or had most notably failed, to measure the 
conductivity of any one metal. The problem which had thus 
proved so difficult has been first solved by Forbes. The absolute 
value which he has found for the conductivity of iron is well guar- 
anteed for accuracy by the full and satisfactory statement of the 
principle and details of his investigation, which has been published 
o 
in the ‘ Transactions.’ Its close agreement with Angstrom’s sub- 
sequent determination, by a very different method, also trustworthy, 
proves the agreement in the conductive quality of the specimens of 
iron used by the two experimenters ; but is not required to confirm 
the results of either. 
“ The method by which Forbes analyses the circumstances con- 
cerned in the transmission of heat along a bar of which one end is 
maintained at a high temperature, is remarkable, no less for the 
ingenuity shown in its invention than for the thorough and vigor- 
ous working out of the laborious processes of experiment and of 
reduction, both graphic and by calculation, which it involves. The 
manner in which, from that analysis, Forbes discovered the varia- 
tion of conductivity, due to variation of temperature, along the bar, 
is very striking. The final deduction of the varying value, through 
a wide range of temperature, of the absolute measure of the thermal 
conductivity of iron, constitutes a very important contribution to 
physical science.” 
After the delivery of the Medal, Principal Forbes took the 
Chair as senior Vice-President. 
The following Communications were read : — 
1. On Some Capillary Phenomena. By Professor Tait. 
This communication was intended to illustrate by experiments 
with the solution of glycerine and oleate of soda, devised by 
Plateau, the mode in which a soap-bubble is detached as a closed 
