( 237) 
XIX—On a Formula representing the Mean Height of the Barometer at the Level of 
the Sea. By Professor HanstEeEn of Christiania, in a Letter addressed to 
Professor ForseEs, Secretary of the Royal Society of Edinburgh. 
OBSERVATORY NEAR CHRISTIANIA, 26th September 1846. 
Srr,—You have communicated to me, that the Royal Society of Sciences in 
Edinburgh has done me the honour to elect me as a corresponding member. I 
beg you to render my humble thanks to the Society, and to assure, that it shall 
be my earnest wish to fulfil every task in my power which the Royal Society 
should demand. 
That this letter may not reach your hands without any scientific communi- 
cation, I subjoin the following :—From November 1822 to April 1824 inclusive, I 
observed the height of the barometer in Christiania, and found the mean reduced 
to 0° R., and to the level of the sea =757™°763 = 335’”-913 lign. de Paris. As the 
mean height of the barometer observed at Paris by Bouvard, and reduced to 0°, and 
the level of the sea is = 337’”53, I was surprised at the great difference of 1-62 
between Paris and Christiania. Ifp denotes the pressure of the atmosphere at 
the level of the sea, m and / the density of the mercury and its height in the 
tube, g the force of gravity, we have p = mgh, and, in another place, p’= mg/h’. 
If f=pisgh=l'’,orl’= . h. Tf, in the first place, the latitude is = ¢, in the 
—e g _ 1—0-0025911 e082 1 ang, taki yc 
second, = ’, we have © = 799095911 cos? 1—0-0025911 (cos 2 p—cos2*”) ; 
h—h' =h, 0:0025911 (cos 2 ?—cos 2 9’). Taking $=0°, ¢’ =90°, we have 
h—h’ = 1-74; and when ¢ = 4850’ (Paris), ¢’ = 59°-55’ (Christiania), we have 
h —h’ = 0/32. But the observations have given for Paris and Christiania 
h—W’ = 162 ; consequently, the mean pressure of the atmosphere is not the 
in different latitudes (“‘ Magazin for Naturvidensk.” 1824, page 282-291). 
Professor ScHouw in Copenhagen has, in the Memoirs of the Royal Society 
of Sciences at Copenhagen for 1832 (page 291-342), collected all the known obser- 
vations of the mean height of the barometer, which, with exactness, could be re- 
duced to the level of the sea, and to 0° R. In the following table I have added 
the result of five years’ observations here at the Observatory, and of the year 
1844.at Bosekop. I have found that the observations can tolerably be represented 
bythe formula 
) = 336-8097 + 13038 cos 2 ¢ — 07478 cos 4 bd — 09145 cos 6 p + 0’-5435 cos 8 @. 

VOL. XVI. PART. III. 30 

