347 
how nearly they agree in settled weather, showing that the 
effect of the two hygrometric corrections is equal and oppo- 
site. 
From the preceding observations, it appears that on wet 
days the barometric formula (II.), corrected statically for the 
hygrometer, gives too great a value for the height. As this 
fact does not appear to have attracted the attention of ob- 
servers, it may be useful to confirm it by other cases which 
have been observed. 
In the following observation of the height of Douce and 
Sugar Loaf, the lower station was at Kilmacanoge cross roads, 
at a point marked on the Ordnance Map as 255 feet, or 42°5 
fathoms. Simultaneous observations were made with a New- 
man’s barometer, which had been carefully compared with my 
own. 
The lower station at Howth was the foot of the cliff in 
Balscaddan Bay :— 
Tasie IV. 
Ther.| Hygr. 
Lower Station. Upper Station. Coeff| Coeff. OBSERVATIONS. 
and foggy at sum- 
mit of Douce. 
0:372'58)28- 153)/0-278)51/1-045 1-011) Aug.31, 1849; va- 
riable. _ 
3. Howth, . .|29:684/0-440/63)29-103,0-419/58/1-058)1-915\June 28, 1852; 
| wet day. 
2. SugarLoaf, |29-635 
eam lak et tpt lad be 
1. Douce, . .|29: a 372|58)27-421/0-361)/50)1-044 1-014) Aug.31, 1849; wet 
In order to compare the heights calculated from these ob- 
servations with the trigonometric heights of the Ordnance 
Survey, we must add 42-5 fathoms for the height of the lower 
station in Nos. | and 2, and two fathoms for the height of the 
lower station in No. 3 above low water of spring tides. These 
corrections have been made in the following Table, in which V. 
denotes the trigonometric heights :— 
