BAROMETRICAL MEASUREMENTS. 
205 
The following are the observations made at Burlington: 
Dates. 
Alt. Ther. 
Det. Ther. 
Cor. Columns. 
1 1 
Aug. 14. 
5h 10^ 
am_ 
18.0 
13.7 
760.43 
Wind NE‘y- 
Cloudy. 
1 2 
do 
7h 40' 
am_ 
18.0 
13.6 
760.53 
do 
do 
1 ^ 
do 
6h 10' 
a m_ 
18.0 
13.9 
760.73 
do 
do 
I ^ 
do 
6h 40' 
am... 
17.9 
14.9 
761.13 
do 
do 1 
1 ^ 
do 
7h 10' 
a m_ 
18.0 
15.2 
761.33 
do 
do 1 
From the little time allowed, in my first observation on the summit, for the mercury to 
acquire the temperature of the air, and for taking the requisite precautions, the result, 47, 
errs in deficiency. The elevation derived from the three sets is 5337*5 above tide, which 
differs from the three results only by 12*2 and 10 feet. 
According to the barometrical measurement by Mr. Redfield and Prof. Emmons, as given 
in the New-York Geological Report of 1838, the elevation of this peak is 5,467 feet. The 
difference between these results is not so considerable as of itself to impair confidence essen¬ 
tially in either, and they should therefore be regarded rather in the light of mutual verifica¬ 
tions, at least so far as concerns barometrical measurement. The justness of this opinion 
may be inferred from some remarks that may follow. If the circumstances of the two mea¬ 
surements were similar, in regard to the delicacy and exactness of the instruments, the posi¬ 
tions of the stations, and the number of observations, the mean of the two should undoubtedly 
be taken. Not having seen a description of Mr. Redfield’s barometers, I can only conjecture 
that they were of the ordinary cistern kind; and if so, the less perfect instruments. 
As to the stations. Prof. Emmons had the advantage of being in nearly the same longitude, 
while mine differed in this respect probably fifty minutes ; but they had the disadvantage in 
their remoteness, mine being about forty and his one hundred miles asunder. The most 
important circumstance in favor of my result, is the number of observations. 
The only other measurement of this mountain, which has come to my knowledge, is a 
trigonometrical one, executed by E. F. Johnson, Esq. a distinguished civil engineer, and 
published Jan. 30, 1839, in his report to the New-York legislature, of his survey of a rail¬ 
road from Ogdensburgh to Lake Champlain. The altitude of Mount Marcy, according to this 
result, is 4,907 feet; which is less than the barometrical measurements make it, by 430 to 
560 feet. This discrepancy is too considerable to be altogether overlooked. 
The fair presumption, as it appears to me, is, that Mr. Johnson sought no greater degree 
of accuracy than was requisite to convey a general idea of its elevation. This may be inferred 
from the fact that its exact determination was a matter of no consequence to the railroad that 
he was exploring, the relation between them being remote and incidental. This presumption 
is strengthened, moreover, from his manner of executing the measurement. His estimating 
the distance to the mountain from a map, instead of deriving it from an accurately established 
