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59
•Tegningen fremstiller Instrumentet klar til Nedfiring;
Tampen af Lod linen hexes i øverste Øiebolt (a) og Loddet
i den nedre (b). Under Nedfiringen løfter Vandtrykket
Propellerne op. saa at Taggerne i Underkant ai
Propel-bosset {c) kommer klar af Taggerne i Muffen, gjennem
hvilken Ventilstangen (d) gaar, og om de ikke kommer ganske
klare, sker Propellens ()mdreiniug med Skraaplanerne, saa
at Muffen og Ventilstangen bliver staaende stille. Naar
Instrumentet derimod under Ophalingen bevæges opad.
driver Vandtrykket Propellerne ned, de dreies rundt den
anden Vei og tager Mufferne med sig. Ventilstængerne,
der ikke kan dreie sig rundt, men styres af Tværstykkerne
(e), skrues da. tilligemed de med Kautschuk overtrukne
Ventiler, mod Ventilsæderne i Enderne af Røret, og naar
de ere næsten lukkede, glipper den sidste Skruegjænge paa
Ventilstangen ud af Skruegjængerne i Muffen, og
Spiral-fjædrene (/) klappe da Ventilerne i, medens Propellerne
og Mufferne gaa løse rundt 0111 den glatte Del af
Ventilstængerne. og frembyder saaledes meget liden Modstand
under Resten af Indhivningen. Instrumentet lukker sig
efter omtrent 7 Favnes (13 Meters) Indhaling. Ringen
om Midten og Skjærmerne rundt Propellerne beskytte
Instrumentet, saaledes at det uden Skade kan ligge paa
Bunden.
For at konstatere. 0111 der var Overskud af Luft i
de nedre Vandlag, blev der over Svikhullet paaskruet et
gjennomboret Laag (g), der ved Hjælp af et Stykke
Gummislange forenedes til et i den ene Ende lukket Glasrør.
Naar Vandet under Nedfiringen strømmede ind i
Vandroret. lob det ogsaa ned i Glasrøret, af hvilket Luften
saaledes blev udjaget. Naar Instrumentet kom ombord,
endevendtes det. saa at Kranen kom ned og Glasrøret op. Man
bevægede nu Vandhenteren lidt frem og tilbage med den
øvre Ende, og hvis der havde været Overskud af Luft,
maatte denne have arbeidet sig op og vist sig i Toppen af
Glasrøret, men dette viste sig stadig fuldt -lige til Tops. og
blev derfor i den sidste Tid ikke paasat."
Instrumentet kan tommes gjennem Tappekranen (/?)
og leverer en Vandprøve paa circa 5 Litre.
Udførelsen af de chemiske Arbeider ombord paa den
norske Nordhavsexpedition overtoges altsaa først i Følge
den oprindelige Plan af Hr. Svendsen, som gjorde Togtet
i 1876 med. men blev senere, da denne af Helbredshensyn
bad- sig fritaget, overdraget Forfatteren, der saaledes har
udført de paa de to sidste Togter gjorte Observationer
delvis med Assistance af Hr. L. Schmelck, som sidste Sommer
medfulgte Expeditionen, og som for Tiden er beskjæftiget
med Bearbeidelsen af en anden Del af det paa Expeditionens
Togter til chemisk Undersøgelse indsamlede Materiale.
The figure shows the instrument ready for sinking.
The end of the sounding-line is made fast to the upper
eye-bolt (a), and the lead to the lower (&). On the
downward passage, the pressure* of the water lifts up the
propellers, enabling the cogs in the under surface of the base
of the latter (c) to get clear of the cogs in the bush,
through which passes the rod of the valve (d); and if not
quite clear, the propeller revolves with the inclined planes,
the bush and the rod of the valve remaining stationary
as before. On the other hand, when the instrument,
on being hauled in, is given an upward motion, the
pressure of the water forces down the propellers, which then
revolve in the opposite direction, carrying along with them
the bushes. The rods of the valves, which cannot revolve,
being kept in position by transverse pieces (e). are. together
with the valves covered with caoutschouc, screwed against
the ends of the tube. Now. when the latter are almost
closed, the last twist of the screw 011 the rod øf the
valve slips out of the corresponding twist of the screw
on the bush, and the spiral springs (/) instantly press
down the valves, the propellers and the bushes revolving
independently round the smooth portion of the rods, thus
presenting but little resistance to the water during the
remainder of the upward passage. The instrument closes
011 being hauled in about 7 fathoms (13 metres). The
ring round the middle, and the shields protecting the
propellers, prevent the instrument from sustaining injury
on its striking the bottom.
With a view to ascertain whether the proportion of
air were really greater in the lower strata, a perforated
cover (g) was screwed over the spigot-hole, and
connected by means of a piece of caoutschouc hose’with a glass
tube, open at one end. Now. when the water 011 the
downward passage flowed into the spiral tube, it also
descended into the glass tube, expelling the air. So soon
as the instrument came on board, it was inverted, the
stop-cock therefore pointing down, aud the glass tube up.
The upper end of the apparatus being now moved a little
backwards and forwards, the surplus of air. if any had
been present, must obviously have forced its way
upwards, and have appeared, in the form of bubbles, at
the top of the tube, which, however, was invariably found
to be quite full, and therefore not attached to the
apparatus when the fact would no longer admit of doubt."’
The stopcock (fx) serves to empty the instrument,
which will hold about 5 litres of water.
The chemical work to be done on board was, as
stated above, originally undertaken by Mr. S. Svendsen,
who went out on the first cruise, in 1876: but, his health
failing, Mr. Svendsen wrfs succeeded by the author, who
had therefore to take the observations instituted in 1877
and 1878. partly with the assistance of Mr. L. Schmelck,
that gentleman having accompanied the Expedition on the
last cruise. (Mr. Schmelck is now engaged in working up
other materials collected 011 the Expedition for chemical
investigation).
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