142 Proceedings of the Royal Society 
this law. But the following values are the most accurate, and 
tend to prove the truth of the law. The apparent discordance in 
the case of iron is in part due to the variations in the qualities of 
that metal in different specimens. 
/8c 
e 
a 
Gold, 
•00001484 
•00001358 
Silver, .... 
•00001796 
•00001809 
Copper, .... 
•00001511 
•00001481 
Platinum, . . . 
•00001006 
•00000851 
Iron, 
•00001573 
•00001220 
In calculating this table, the values of c from the experiments 
of M. Wersheim are used; those of a from the experiments of Mr 
Mathiessen (except iron); those of ft from the experiments quoted 
by Prof. Balfour Stewart in his Text-Book; and the assumed 
temperature is 18° C., or 283° absolute temperature. 
2. Notice of the Completion of the Works designed by Sir 
Charles A. Hartley, F.R.S.E., for the Improvement of the 
Danube. By David Stevenson, Esq., V.P.R.S.E. 
In 1868 I presented to the Society, on behalf of Sir Charles A. 
Hartley, a memoir published by the European Commission of the 
Danube, on the improvement of that river, and at the same time 
gave a notice of the works designed by Sir Charles Hartley for 
effecting that important object. These works have now been com- 
pleted, and Sir Charles Hartley has again asked me to present to 
the Society a second memoir published by the Commission, which 
brings the history of the works constructed under their charge down 
to the time of their completion in 1873. 
In supplement of the notice formerly communicated, which 
referred to a work in progress, it may not be uninteresting, now 
that the work is completed, to state briefly what has been effected 
by this most important and successful example of hydraulic 
engineering. 
