For hver af disse Dage udtoges af Karterne Baro- 
meterhøjden for en Række Punkter paa Havet, nemlig: 
Nord. Bredde (Zat. N) 60° 65° 
Lenede f. Gr. (Long. from Gr.) 30° W 30° W 
Nord. Bredde (Lat. N) 650 70° 
Leenede f. Gr. (Long. from Gr.) 0? 09 
Af disse Tal beregnedes Maanedsmiddel for den Aar- 
række, hvori hver Maaned forekommer. (Januar til August 
3 Aar, September til November 4 Aar, December 3 Aar). 
For de tilsvarende Tidsrum beregnedes Maanedsmiddel 
af Barometerstanden for Stationerne Stykkisholm, Akureyri, 
Berufjord, Thorshavn, Mandal. Skudesnes, Bergen, Florø, 
Aalesund, Christiansund, Brono, Bodo, Tromsø, Alten og 
Vardø. Disse Media for Epoken 1873—76 eller 1873—75 
eller 1874—76 subtraheredes fra de normale Maanedsmedia 
efter den 24- eller 16-aarige Række. De fundne Differentser 
tjene til at reducere den kortvarige Række efter Karterne 
til Kyststationernes normale Værdier. 
For Kyststationerne toges for Karternes Epoke Maa- 
nedsmiddel af Barometerhøjden Kl. 8 Morgen. Disse Medier 
subtraheredes fra de normale Maanedsmedia. Differentsen 
tjener til at reducere Karternes Observationer fra Kl. 8 
a.m. til Dagsmediet. 
Begge de saaledes udledede Correctioner for hver 
Kyststation sloges sammen. 
Til Reduction af Barometerstanden paa en Hav-Station 
til den normale Barometerhøjde anvendtes i Regelen de 
tilsvarende Correctioner for flere Kyststationer, og disse 
gaves ved Beregningen af det endelige Resultat en Vægt, 
der var omvendt proportional med Afstanden mellem Hav- 
Stationen og den respective Kyst-Station. 
Det var ikke muligt, for alle de ovennævnte Hay- 
Stationer, at erholde af de synoptiske Karter fuldstændige 
Observationsrækker. I saadanne Tilfælder har jeg com- 
pletteret Rækkerne, dels ved at construere Karter for de 
enkelte Maaneder og udfylde Hullerne derefter, dels ved 
at eonstruere Curver for hver Hav-Station, der viste Luft- 
trykkets normale aarlige Variation fra Maaned til Maaned, 
og paa den Maade interpolere de manglende Værdier. 
Disse Curver bave ogsaa været særdeles nyttige for de 
complette Hav-Stationers Vedkommende til at controllere 
de udledede Normalværdier, idet deres almindelige Character 
maatte variere successivt langs Forbindelseslinierne mellem 
Kyststationerne paa begge Sider af Havet, og henimod 
Kysterne nærme sig til Kyststationernes. 
Hav-Stationernes Barometerhøjder vare allerede redu- 
cerede til Hayfladen. Land-Stationernes bleve reducerede til 
Havfladen, idet Hensyn toges til Lufttemperaturen. 
Endelig reduceredes samtlige Barometerhøjder til ab- 
solut Lufttryk eller til den normale Tyngde (ved 45° 
Bredde og Havfladen) efter Formelen: 
60° 
202 W 
I 
For each of these days, I took from the charts the 
height of the barometer for a series of points on the 
sea, viz.: — 
70° 609 650 70° 750 609 
200W 100W 100W 100W 610° W 09 
65° 70° 750 15° 709 70° 
10H 10°K 10K 900B 40°R 50°R, 
From these figures was computed the monthly mean 
(Jan- 
uary to August 3 years, September to November 4 years, 
for the series of years in which each month occurs. 
December 3 years). 
For the corresponding periods was computed the mean 
monthly height of the barometer for the Stations Stykkis- 
holm, Akureyri, Berufjord, Thorshayn, Mandal, Skudesnes, 
Bergen, Florø, Aalesund, Christiansund, Brønø, Bodø, 
Tromsø, Alten, and Vardø. These means for the interval 
1873—1876 or 1873—1875 or 1874—1876 were subtracted 
from the normal monthly means deduced from the twenty- 
four or the sixteen-years series. The differences thus found 
serve for reducing the short series of the charts to the 
normal values of the Coastal Stations. 
For the Coastal Stations, were taken the monthly means 
of the height of the barometer at 8 a.m. for the period 
of the charts. These means subtracted from the 
normal monthly means. The difference serves for reducing 
the observations in the charts from 8 a.m. to the daily mean. 
Both the corrections thus deduced for every Coastal 
Station were added together. 
For reducing the height of the barometer at a Sea- 
were 
Station to the normal height, the corresponding correc- 
tions for several Coastal Stations were as a rule applied, 
and these were given, when computing the final result, a 
weight inversely proportional to the distance between the 
Sea-Station and the respective Coast-Station. 
It was not possible to obtain for all the above- 
mentioned Sea-Stations of observations 
from the Synoptical Charts. 
the series myself, partly by constructing maps for the dif 
ferent months and then filling up the blanks, and partly 
by drawing curves for each Sea-Station that exhibited the 
complete series 
In such cases I completed 
normal annual variation from month to month of the atmo- 
spheric pressure, and thus interpolating the missing values. 
These curves have also proved exceedingly useful as regards 
the complete Sea-Stations, viz., in controlling the computed 
normal values, since their general character could not but 
vary successively along the lines of connexion between the 
Coastal Stations on both sides of the sea, and, in the vicinity 
of the coasts, approach that of the Coastal Stations. 
The height of the barometer for the Sea-Stations had 
been already reduced to the sea-level. When reducing it 
for the Land-Stations to the sea-level, regard was had to 
the temperature of the air. 
Finally, every height of the barometer was reduced to 
absolute atmospheric pressure, or to the normal gravity 
(45th parallel of latitude and sea-level), according to the 
formula: — 
