nN 
_— 
ad 
In this formula / is supposed to be the mean tension of 
vapour in the column. ‘This modification of the formula was 
proposed by Mr. Rennie, in a paper read. before the Academy, 
and which is now in course of publication. 
The average result of the ten observations seemed to agree 
best with formula (1.); from which it would appear that the 
vapour in the air entered into the physical consideration of the 
question in so uncertain a manner, that, on the whole, it was 
safer to leave it out. 
Mr. Galbraith stated that if proper precautions were used 
in the determination of the tension of the vapour at the two 
stations, it was not unlikely that formula (11.) would give 
results much more in unison with the levelled height than 
those he had already obtained. 
By applying Mr. Rennie’s modification, the heights are 
necessarily increased, and as the average height calculated 
from formula (1.) exceeded the true, formula (111.) should, on 
practical grounds, be excluded. 
Mr. Galbraith made some observations on the coeflicient 
10000, and gave a full account of the various constants on 
which it depended. | 
The paper was referred to the Council for publication. 
The following donations to the Museum were presented : 
1. An iron stirrup, found in the river Boyne, at New 
Haggard Ford, above Trim; presented by Michael Odlum, 
Esq. 
2. A token of Edward Marttin of Drogheda, found in a 
field at Moygaddy, county of Meath, near Maynooth ; pre- 
sented by the Duke of Leinster. 
’ 
VOL. VI. 25 
