; H. A. Hazen—Reduction of Air-pressure to Sea-level. 457 
For 1000’ :C = 171675 —0".0389 (30" — p) — 0"-00245 (t~ 32°) 
0"-0000065 (t—32°) (¢ —52°) 
For 2000’: OC = 2":3803 —0"-0794 (30” — p)—0"-00490 (¢—32°) 
+ 0’:0000130 (¢—32°) (¢—52° 
For 3000’: C = 3"-6401 — 071214 (30” — p)—0"-00735 (t—32°) 
4 07-0000195 (t—32°) (¢—52°) 
The temperature term might have been much simplified, but 
this harmonizes best with later work. These formule were 
constructed up to an elevation of 8,000’, and from a combina- 
tion of the eight the following general formula was obtained: 
C = -0000000000003A 
+ [":000000021702 — 0"-0000000008(30" — p) |h* 
0”:001145482 —0”:0000381 (30" — p) 
—0"-00000245 (t—32°) + 0"-0000000065 (¢—-32°) (¢—52°) |r 
in whieh C = reduction to sea, / is hight of station in feet, p 
is pressure at station, and ¢ the mean temperature at the time 
of observation, between station and sea. 
If, now, we assume a pressure of 30” and consider the total 
hight above such a pressure, as proposed by Prof. Angot, of 
aris, we may put 80’—p for C 1 : 
solving for h obtain the following expression, which is general 
for any altitude: 
n/4b xX (30" —p) -a'—a 
4b X (30 =p) bens ~ 0"-00000000038h" (1). 
h 
° 
in which w= 07001145482 — 0”:00000245 (¢ —32°) 
++ 00000000065 (t— 32°) (t~52°) — 00000381 (30"—p) 
and b = 0"-000000021702 — 0”:0000000008 (30”— p). 
e formula a slight change from a rigid 
value of Laplace has been made for a known variation at Mt. 
—_ 
=] 
ie) 
ro) 
=] 
i] 
ct 
br] 
i] 
Q 
g. 
i=} 
0g 
+ 
a 
Of) Ap ieete 
formule is given in Table ITI. 
The results in column 4 vary the most, and show, as has 
already been suggested, that no general formula can be deter- 
he . h . 
with which the original formula of Laplace may be modified 
for different places, also the accuracy of this general method 
of procedure. May it not be possible to determine a general 
formula from the actual observations in different places, which 
shall require but a slight and readily-determined change to 
make it applicable to any locality 
_ Am. Jour. ea meen eno Von. XXI, No, 126.—Junz, 1881. 
a eo 6 We” O82 be rooted ee 2 de ts id oe 
