48 



Sættes Coefficienten M hg 1. Kvartmilen lig '/go af en Ækva- 

 torsgrad og g Lig 9. '"810 (50° N. Br.), såa faar man den 

 følgende Tabel for Skalaens Inddeling. 



ficient M to equal 1. a mile to equaJ ' , ; „ of an equatorial 

 degree, and g to equal 9.810'" (in lat. 50" N.), we have 

 the following series of figures for graduating the scale. 



Vil man etterse, om Roret gjenném Bunden er i ( )r- 

 den. stænges Kranen d, Pakningsstykket / afskrues. og Bly- 

 røret bøje's noget til Side ; man løsner paa Pakningsringen 

 c, Roret a løftes op. indtil dets nedre Ende har passeret 

 Kranen paa Roret b, hvoretter denne afstænges, og Roret 

 a kan lottes helt op og eftersees. 



Ved Brunen af Vandloggen maa to Ting haves i 

 Erindring: 



1) at Skalaens Xulpunkt eller rettere Snorens Længde fra 

 Flyderen til Vægten, der tjener til Viser paa Skalaen, 

 retter sig efter Skibets Dybgaaende, : og 



2) Pejlen, der foraarsages ved stadig Krængning. 



Med Hensyn til det første Punkt, reguleres dette 

 lettest derved, at man standser Skibets Fart. udtager Træ- 

 kilen og Hytter Loddet paa X ul. Det hele kan udføres i 

 nogle Minutter. Ved de hyppige Stopninger, som Lodning 

 og Skrabning foranledigede, kunde vi paa Nordhavs-Expe- 

 ditionen altid holde Vandloggen skarpt justeret. Paa Sejl- 

 skibe vil Forbruget ombord ikke saaledes forandre Dyb- 

 gaaendet, som paa Dampskibe, men man bør dog imellem 

 foretage et Par nøjagtige Logninger med den almindelige 

 Log og Uhr, for at kontrollere Vandloggen og eventuelt 

 justere den paany. 



Ved BO" Bredde med g — !).""X!0 bliver Skalastregen for 12 



Miles Farl 1.945 Meter, altsaa kun 1 forskjellig fra Tabel 



lens. Fm- de mindre Ea tij heder bliver Forskjellen forholds- 

 vis mindre. 



To ascertnin whether the tube passing through the 

 ship's bottom be in order, the stopcock f? is turned back. 

 the gland / screwed off. and the leaden tube bent a little 

 aside; then. after partially unscrewing the gland r. the 

 tube a is lifted up till its lower extremity is just clear of 

 the cock of the tube b, and when this too has been 

 turned back. the tube a may be tåken out and examined. 

 When using the water-log, two titings must be borne 

 mind. viz. — 

 Th.it the position of zero on the graduated scale. or 

 rather the lengtb of the line from the float to the 

 weigbt which plays against the scale. is regulated by 

 the draught of the ship ; and 

 The heeling error. 

 As regards the first source of error. the index is best 

 regulated by stopping the vessel, and then. after taking out 

 the wooden wedge, placing the weight at zero. This may 

 be done in a few min ut es. With the frequent stoppages 

 involved in sounding and dredging on the North-Atlantic 

 Expedition. we could always rna nage to keep the water-log 

 accurately adjusted. In sailing-vessels the draught is not 

 of course .as in steamers affected by the consumption of 

 coal; but now and then the speed should nevertheless be 

 closely determined with the common log .-in a means of 

 testing the results of the water-log. and. il' iiecessary. of 

 adjusting that instrument anew. 



in 

 1) 



2) 



ln lat so" x., where g = S).S30 m , the division . m the scale 

 denoting a speed of i- knots «ill cowespond to 1.94")°', 

 and iliu^ exhibit a difference of only 1""" as compared with 

 the figures in the Table. For less velocities, the difference 

 will be proportionallj reduced. 



