Skrue uden Ende drejer Hjulet b, der har 28 Tænder. 
Concentrisk med b og fast i dette er Drevet c, der har 8 
Tænder. Dette drejer igjen det store Hjul eller Skiven a, 
som har 80 Tender. Følgelig svarer 10 Omdrejninger af 
b til 1 Omdrejning af a. 28 Omdrejninger af Verticalaxen 
give en Omdrejning af b. 280 Omdrejninger af Vertical- 
axen give 10 Omdrejninger af b og 1 Omdrejning af a. 
Sættes altsaa n = 280, have vi 
vo =f + 0.08216 x 280 = f + 23.00. 
Skiven a er nu inddelt ved radiale Streger paa Ran- 
den i 23 ligestore Dele, og hver Del mellem disse ved 
Punkter i Femtedele, saa at Tiendedele med Lethed kunne 
aflæses. Dersom Viseren 7, der staar fast paa as Omdrej- 
ningsaxe, viser paa 0 før Registreringen, vil den, efter en 
Registreringstid af 30 Secunder, ligefrem angive Værdien 
af 0.08216 n eller v—f, eller med andre Ord Vindhastig- 
heden minus Frictionscoefficienten, udtrykt i Meter pr. Se- 
eund. For at faa den sande Vindhastighed, behøver man 
følgelig kun at stille Skiven saaledes, at Viseren staar paa 
0, lade Instrumentet, udsat for Vinden, registrere 1 30 Se- 
cunder, aflæse hvad Viseren peger paa og dertil lægge 
Frictionscoefficienten. 
Registreringen i et bestemt Tidsrum iverksættes paa 
følgende Maade. Hjulene a, b og c dreje sig om faste 
Axer, der sidde paa Armen ef. Denne er bevægelig, idet 
den ved sin øvre Ende, ved e, kan drejes om en i Instru- 
mentets Bagvæg ' fastgjort horizontal Axe, medens dens 
nederste Del trækkes stadig tilhøjre (i Retning af Pilen 
Fig. 6) af en Metalfjeder g. Naar derfor Instrumentet 
ikke registrerer, griber Hjulet b ikke ind 1 Gjængerne paa 
Skruen uden Ende paa Verticalaxen, men denne drejer sig 
ganske frit med Halvkuglekorset. lagttageren tager Instru- 
mentet i Haanden, som Fig. 5 viser, med Tommelfingeren 
paa Knappen h, men uden at trykke paa denne, og løfter 
det i Vejret med Axen vertical. Halvkuglerne gaa nu frit 
rundt med Vinden. I det Øjeblik Uret viser 0 Secunder, 
trykker han Knappen ind. Armen ef med de tre Hjul 
flyttes ind mod Verticalaxen, Tænderne paa Hjulet b gribe 
ind i Skruen paa denne, Hjulene b, c, og a sættes i Bevæ- 
gelse: Registreringen begynder. Den fortsættes, idet Knap- 
pen h holdes trykket ind, i 30 Secunder. Naar denne Tid 
er forløben, slippes Tommelfingeren løs fra Knappen h, 
Fjederen virker og flytter b fra Skruen uden Ende, og 
Registreringen standser. 
Tandhjulet d har et dobbelt Øjemed. Naar Registre- 
ringen standser, gribe Tænderne paa Hjulet b ind i Tæn- 
derne paa d og dette virker som en Stopper eller Bremse 
til at holde Tællerverket fast, saa at Aflæsningen kan fore- 
tages senere og hvorsomhelst. Ved at dreje paa Knappen 
s paa Bagsiden af Yderkassen (Fig. 7) drejer man ogsaa 
Hjulet d og lagttageren kan saaledes, uden at aabne Kas- 
sen, dreje Hjulene b, c og a og bringe Viseren til at pege 
paa 0. 
Som man ser, er Instrumentets Construction saadan, 
at det med Lethed kan bruges ogsaa om Natten. Med 
Knappen s stilles, f. Ex. inde i Bestiklugaren, Viseren paa 
0, Instrumentet tages ud og holdes op færdigt til Obser- 
axis turns the wheel b, which has 28 teeth. Concentric 
with b is a cogwheel c, with 8 teeth, which turns the large 
wheel or disk a, furnished with 80 teeth. Consequently, 
10 revolutions of » correspond to one revolution of a; 28 
revolutions of the vertical axis correspond to one revolution 
of b, 280 revolutions of the vertical axis to 10 revolutions 
of b and one revolution of a. Hence, putting n = 280, 
we have 
v =f + 0.08216 < 280 =f - 23.00. 
The dial a is accordingly divided by radial lines on 
its limb into 23 equal parts, and each part by dots into 
fifths, so that tenths can easily be read off. If the hand, 
or index, 7, which is fixed to the axis of a, points to zero 
before registration, it will, after an interval of 30 seconds, 
indicate the value 0.08216 m, or v—f, that is the veloc- 
ity of the wind minus the friction coefficient, expressed in 
metres per second. In order to get the true velocity of 
the wind, we have, therefore, only to place the dial so that 
the index points to zero; let the instrument, exposed to 
the wind, register for 30 seconds; and then read off the 
indication of the hand, adding to this number the value 
of the friction coefficient. 
The registration in a definite interval of time is per- 
formed as follows. The wheels a, b, and ¢ have their axles 
fixed to the arm e f. This arm is moveable, turning as it 
does at the upper end, at e, about a pivot in the hind 
part of the instrument. whereas its lower end is constantly 
drawn to the right (in the direction of the arrow, Fig. 6) 
by the metallic spring g. When, therefore, the instrument 
is not registering, the teeth of the wheel > do not bite in 
the endless screw on the vertical axis; both are quite free 
and revolye with the cups. The observer takes the instru- 
ment by the handle, with his thumb resting lightly on the 
button (as shown in Fig, 5), and then raises the instru- 
ment, with its axis in a vertical position. The cups now 
revolve freely with the wind. At 0 seconds by the obser- 
ver's watch, he presses the button inwards, the arm ef with 
the three wheels is moved towards the vertical axis, the 
teeth of the wheel } bite in the endless screw, b, c, and a 
are put in motion, and the registration begins. It is con- 
tinued for 30 seconds, the button h being kept pressed in. 
After the expiration of this interval, the observer removes 
his thumb from the button h, the spring acts. removes b 
from the endless screw, and the registration stops. 
The toothed wheel d serves two purposes. On stop- 
ping registration, the teeth of the wheel å bite into the 
teeth of the wheel d, which acts as a stopper or break, 
and keeps the wheelwork steady,.so that the reading of 
the dial may be made at any time or place afterwards. 
On turning the button s at the back of the outer case 
(Fig. 7), the wheel d is also turned with it, and the obser- 
ver can thus, without opening the case, turn the wheels %, 
c, and a, and adjust the index to zero. 
As will be seen, the construction of the instrument 
is such as to admit of its being used with facility at night. 
By means of the button s, for example, the index is ad- 
justed in the Deck-house to zero. The instrument is then 
