20 



er af Vigtighed for Nøjagtigheden af den følgende Bereg- 

 ning af Dybden. Det Stykke af Lodlinen, der er mellem 

 Rullen og Fodblokken, maa altid have en passende Stram- 

 ning, saaat Linen ikke under Bevægelsen slaar Bugter, der 

 kunde bringe den til at kaste sig om en eller anden frem- 

 staaende Gjenstand og derved foraarsage Havarier eller en 

 pludselig Standsning af Lodlinens Bevægelse. Denne Brems- 

 ning fordrer derfor baade Opinerksomhed, Kraft og Øvelse. 

 I 1877 forsøgte jeg en mekanisk Bremse paa Rullen, 

 men den viste sig upraktisk og anvendtes kun nogle Gange. 

 Naar Skibet lotter sig paa Soen. rives Linen af Rullen 

 med stor Kraft, og naar det atter sænker sig. formindskes 

 Loddets Drag. ja ophæves undertiden næsten for et Øje- 

 blik. Disse uafladelige Forandringer foles strax. naar man 

 bremser med Haand, og med nogen Øvelse vænner man sig 

 til at bremse netop det nødvendige, men med den mekani- 

 ske Bremse viste det sig ugjørligt at følge Forandringerne, 

 der ikke føltes gjennem Apparatet. 



Ved Dybder, der ikke oversteg 900 til 1000 Favne. 

 mærkedes bedst, at Loddet slog i Bund. derved, atman 

 lod Linen løbe ganske løst gjennem Haanden. og man følte 

 da en pludselig Aftagen i Udløbshastigheden. Man kunde 

 ogsaa tydelig se det derved, at Linen mellem Fodblokken 

 og Rullen lagde sig pludselig fiad ned paa Dækket. Saa- 

 snart over 700 Favne var ude, var den Bremsning, der 

 udfordredes for at holde Linen stram, kun ringe. I nogle 

 faa Tilfælder, i hvilke der blev loddet paa 1100 til 1200 

 Favne med Rorlod alene, viste det sig, at det ikke var 

 muligt at iagttage det Øjeblik, da Loddet kom i Bund. 

 Linen vedblev at løbe ud paa Grand af sin egen Vtegt 

 med en Hastighed, der ikke var synligt forskjellig fra den 

 Hastighed, hvormed den lob med Loddet som Tillægsvægt. 

 Under saadanne < )mstandigheder loddedes om igjen med 

 Baillie-Maskine, dersom det ausaaes fornødent at faa et 

 nøjagtigt Lodskud. Med Rørlod og AVilles Vandhenter 

 sammen kunde der faaes gode Lodskud paa over 1100 Favne, 

 som et Forsøg paa Station 247 viste. Her gav nemlig 

 Baillie-Maskinen 1120 Favne, medens Rorlod med Vand- 

 henter gav 1124 Favne. 



Bestemmelse af Dybden. Da Lodlinen for de større 

 Dyb kun var mærket for hver 100 Favne, maatte det nøj- 

 agtige Favnetal soges ved særegne Observationer og Bereg- 

 ninger. Den fra først af brugte Fremgangsmaade var føl- 

 gende. I det Øjeblik. Loddet gik i Våndet, og naar et 

 Hundrede-Favne-Mærke gik i Våndet, raåbtes „Nu" og 

 Klokkeslettet noteredes i Loddejournalen paa nærmeste 

 Sekund. Foral give Noteringerne større Sikkerhed, var- 

 skoedes af Kulkene ved Rullen altid i For.vejen ..Mærke", 

 naar e1 af Mærkerne gik af Hullen. I det Øjeblik Loddet 

 var i Bund, raabtes „Bund" og det tilsvarende EQokkeslet 

 noteredes. Ai Rækken af de under hverandre noterede 

 Klokkeslet toges første Differents. Disse Tal stige med 

 Dybden, idet Udløbshastigheden aftager med Længden af 

 den gjennem Vandel løbende Lodline. Dernæst beregnedes 



presented in Fig. 14. The two men witb leather gloves 

 eildeavoured. by pressing upon the reel, to keep the motion 

 as uniform as possible, this being an essential condition 

 for accurately computing the depth. When veering. the 

 line between the reel and the leading-block must be kept 

 sufficiently taut. to prevent its running out in bights. 

 that might catch on same projecting object. and thus 

 occasion damage. or possibly a sudden stoppage of the 

 line. Hence, skilful braking requires care. practice. and 

 physical strength. In 1877 I tried a mechanical brake: it 

 proved. however, inetticient. and was used only a few times. 

 When the vessel heaves. the line is run off the reel with 

 great violence, and on her plunging into the trough of a 

 sea. the drag of the lead becomes greatly diminished, nav, 

 for a moment may be tåken off altogether. These constant 

 alternations are instantly felt when the braking is done by 

 haud; and with some little practice. the brakesmen can 

 calculate to a nicety the needful amount of pressure. where- 

 as with the mechanical brake ve found it impossible to 

 follow the changes, which could not be felt through the 

 machine. 



In depths not exeeding 900 or 1000 fathoms, the best 

 way of determming the exact moment when the lead struck 

 the bottom, was to let the line run loosely through the 

 hand. when a sudden disminishment of velocity would be felt. 

 Nay. it could be distiiictly seen, the line between the lea- 

 ding-block and the reel becoming all at once slack and 

 dropping down on the deck. Having veered to a depth 

 of 700 fathoms. there was no great need of braking to keep 

 the line taut on the remainder of the downward journey. 

 In some few instances. when sounding in from 110<t to 1200 

 fathoms with the tube-lead alone, we found it impossible 

 to tell exactly when the lead touched the bottom. The 

 bne went on running out by its own weight only. and more- 

 over. with a velocity that did not sensibly (lifter from that 

 given it by the additional weight of the lead. Hence. when 

 accuracy of measurement was the chief desideratum, we had 

 to sound again, and with the Baillie machine Sent down 

 along with Wille's water-bottle. the tube-lead gave good re- 

 sults, as shown at Station 247. Here, the Baillie machine 

 indicated a depth of 1120 fathoms. and the tube-lead used 

 with AYille's water-bottle. 1124. 



Determination of Depth. — The line for deep-sea soun- 

 dings being graduated into hundreds of fathoms. the exact 

 depth bad in each case to be computed from special ob- 

 servations. ( Jur mode of procedure was. at first, as follows: ■- 

 The moment the lead entered the water, as als,, øne of the 

 slips of bunting on the line. an officer called out. and 

 the time to a second was entered in the sounding-journal. 

 To attain greater accuracy, the brakesmen had to give 

 timely notice for every slip of bunting run off the reel; the 

 instant the lead struck the bottom, the officer gave the 

 word, aud the time \\;is entered in the journal. Krom the 

 series of entries was computed the first difference, " or sel of 

 intervals. These figures increase with the depth, the velo- 

 eil\ diminishing with the Length of the line running out 

 through i he water. The second difference of the series 



