662 Mr. E. W. Morley on the Vapour-Pressure 
An inspection of the curves shows that any change of that 
order could not fail to be detected. 
In conclusion, I desire to express my best thanks to 
Professor Pollock for many valuable suggestions and for 
his continued encouragement during the work. 
The University of Sydney. 



LXXIII. On the Vapour-Pressure of Mercury at Ordinary 
Temperatures. By Epwarp W. Moriey”. 
if 1890, when attempting to determine the density of 
hydrogen with accuracy, it became convenient to know 
the vapour-pressure of mercury at ordinary temperatures. 
There were extant two series of actual measurements at such 
temperatures, and four computations of the desired values 
from extrapolation formule founded on observations at higher 
temperatures. 
The first of these computations was due to ReegnaultT, and 
was published by him in 1862. A second and a third were 
published by Hagent and by Hertz§$ in 1882. Ramsay and 
Young || published the fourth in 1886. 
Regnault also made a few observations at temperatures 
below 100°, which were published with those mentioned 
above. They seem to have been of service only in guiding 
conjecture as to the vapour-pressure which was assumed for 
O°. Lastly, van der Plaats{] in 1886 published direct deter- 
minations of the vapour-pressure at 0° and at the temperature 
of his laboratory. 
The following table gives the vapour-pressure of mercury 
at certain temperatures according to these authorities :— 







| = | 
| : i r 
| Temp.| Regnault. Hagen. Hertz. vo | eee 
baer mm. mm. mm. mm. mm. 
0 0-0200 0:015 0:00019 bs 0:0047 
Lo 0:0268 0-018 0-0005 sui 0-008 
20 0:0372 0-021 0:0013 
30 00530 0-026 0 0029 
40 00767 0:033 — 0:0063 0-008 
50 0:1120 0-042 0-013 0-015 



* Communicated by the Author. 
+ Relation des Expériences, ii. p. 506. 
t Wiedemann’s Annalen, xvii. p. 618. 
§ Ibid. xvii. p. 197. 
|| Chem. Soc. Journal, xlix. p. 37. 
qi Recueil des Travaux Chimigues des Pays-Bas, v. p. 149. 
