vation. Med et almindeligt Lommeur, der slaar 5 Slag 
i 2 Secunder, for det venstre Øre, og Vindmaaleren i højre 
Haand trykker Iagttageren paa Knappen Å og teller i 
samme Øjeblik 0. Naar han har talt 75 Slag af Uret, ere 
30 Secunder forlobne, og Knappen slippes. Instrumentet 
bringes ind i Bestiklugaren og aflæses. 
Med Hensyn til Instrumentets Construction bemerkes 
forøvrigt Følgende. Korset, der bærer Halvkuglerne, er 
fæstet til Verticalaxen med en Skrue, der ved en Fjeder, 
som eriber i et Indsnit i denne, er hindret fra at skrue 
sig løs. En liden eylindrisk Kappe lige under denne Skrue 
drejer sig rundt med Axen og hindrer Regndraaber fra at 
komme ned langs Axen. Halvkuglerne ere fæstede til 
Armene med sterke Skruer, saa at de ikke let kunne løsne 
og blæse bort, og holdes tillige af dem i den rette Stilling 
og Afstand. Tællerverket er indesluttet i en Metalkasse, 
der paa Forsiden har en Dør med et lidet Vindu, gjennem 
hvilket Aflæsningen paa Skiven kan ske, uden at Kassen 
behøver at aabnes. Ved at aabne Døren kan man med 
Lethed komme til de enkelte Dele af Verket for at rense 
eller smøre dem. I Bunden af Kassen er en firkantet 
Aabning, netop stor nok til den fornødne Bevægelse af 
Armen e f, hvilken herved er reguleret til de bestemte 
Grændser til begge Sider. Den øverste Del af Haandtaget 
er en hul Metaleylinder, 1 hvilken den nederste Del af 
Armen e f med Knappen h bevæger sig. I denne Cylinder 
er Træhaandtaget indskruet og lukker saaledes forneden for 
Tællerverket. * 
Instrumentets Frictionscoefficient bestemtes, saa ofte 
der var Anledning dertil, ved i ganske stille Vejr at lade 
Vindmaaleren registrere den ombord følte Vindhastighed, 
medens Skibets Hastighed observeredes efter Vandloggen, 
som nedenfor skal beskrives. Ved disse Bestemmelser maa 
man passe nøje paa, at Luften under Registreringen er 
aldeles rolig. Et Kjendetegn herpaa er, at Nøens Overtlade 
ikke viser den mindste Krusning. Men dette Tegn maa 
være af nogen Varighed, for at man skal være sikker, thi 
de første Vindpust gaa henover Søens Spejl uden synlig 
Virkning. Kommer Vindpustene fra Siden, har man et 
sikkert Merke deri, at Røgen fra Skorstenen ikke viser 
nøjagtig ret agterover. 
/ 
Tagttagelserne til Bestemmelse af Frictionscoefficienten 
vare følgende. 
1877. 
Log. Vindmaaler. 
Datum. Kvartmil | Meter Meter Frictions- 
i Timen. | pr. Secund. | pr. Secund. | Coefficient. 
Juni 15 TR 4.0 2.5 + 1.5 
~ 80 eae || 3-7 Doll 1.6 
Tr FoR 3.8 QD 1.6 
Juli 15 7.0 3.6 oy? 1.9 
Middel 1.65 
Den norske Nordhavsexpedition. H. Mohn: Meteorologi. 
| 
taken out on deck and held up ready for observation. 
Holding to his left ear an ordinary watch (5 beats in 2 
seconds), and having in his right hand the anemometer, the 
observer presses the button h, counting as he does so 0. 
Having: counted 75 beats of the watch, 30 seconds will 
have elapsed, and the thumb is removed from the button. 
The instrument is then taken imto the deck-house and the 
reading made. 
With regard to the construction of the instrument, 
the following additional remarks are appended: — The cross- 
bars supporting the cups are fixed to the vertical axis by 
means of a screw, which a spring, that fits into an incision 
in the latter, prevents from screwing itself loose. A small 
cylindrical collar, placed immediately beneath this screw, 
revolves with the axis, and prevents drops of rain from 
trickling down it. The cups are fastened to the arms with 
strong screws, to prevent them from loosening and blowing 
away, as also to keep them in the right position and at the 
right distance. The wheelwork is adjusted in a metal case, 
having in front a door with a small window, through which 
the reading on the dial can be made without the necessity 
of opening the case. On opening the door, the wheelwork 
can be easily got at, to be cleaned or oiled when required. 
In the bottom of the case there is a rectangular opening, just 
sufficiently large to admit of the free motion of the arm 
e f, which is accordingly kept on both sides within the 
proper limits. The upper part of the handle consists of a 
hollow metal cylinder, in which moves the lower part of 
the arm ef with the button %. Into this cylinder is 
screwed the wooden handle, closing in accordingly the 
wheelwork from below. 
The friction-coeffictent of the anemometer was deter- 
mined as frequently as opportunity offered, by registering 
in perfectly calm weather the velocity of the wind as felt 
on board, the rate of the ship being simultaneously taken 
from the water-log, to be described in the sequel. When 
performing these determinations, the greatest care must be 
taken to ascertain that the air is quite calm during regis- 
tration. A good proof is afforded by not even the faintest 
breath of air curling the surface of the sea. But this sign 
must be of some duration, to give perfect certainty, since 
the first puffs of wind pass over the surface of the sea 
without producing the slightest visible effect. When the 
puffs of wind are on the beam, the observer has a sure 
sign in the smoke from the funnel not passing straight aft. 
The observations for determining the friction-coefficient 
of the anemometer were as follows: — 
1877. 
Log. Anemometer. 
Date. Naut. Miles Metres Metres | Friction- 
an Hour. | per Second. | per Steen | Coefficient. 
June 15 ion | 40 ae | de ng 
» 20 7.2 | Br 2.1 1.6 
Ris on 75 | 3.8 QD 1.6 
July 15 7.0 | 3.6 7 1.9 
Mean 1.65 
bo 
