The cruise of Her Majesty's ship "Challenger" : voyages over many seas, scenes in many lands . rrying out similar results were employed withequal success; they consisted usually of a brass tubeabout 3 inches in diameter and from 2 to 3 feet inlength, fitted at either end with stop-cocks connected APPARATUS AND APPLIANCES USED. 49 to each other by means of a rod on which is a move-able float. When lowered to any desired depth,both cocks being open to allow the column of waterto freely pass through, immediately the motion of Fig. 6. m 1 1 1 MM k I I I ill 11H ! 1 i i I1 ^ 1 11 in L l lowering is
The cruise of Her Majesty's ship "Challenger" : voyages over many seas, scenes in many lands . rrying out similar results were employed withequal success; they consisted usually of a brass tubeabout 3 inches in diameter and from 2 to 3 feet inlength, fitted at either end with stop-cocks connected APPARATUS AND APPLIANCES USED. 49 to each other by means of a rod on which is a move-able float. When lowered to any desired depth,both cocks being open to allow the column of waterto freely pass through, immediately the motion of Fig. 6. m 1 1 1 MM k I I I ill 11H ! 1 i i I1 ^ 1 11 in L l lowering is reversed and hoisting commenced, theflat float being pressed on by the weight of waterabove it, shuts both cocks simultaneously, and soincloses a specimen of the water at that particulardepth. 50 CBUISE OF CHALLENGED. The thermometers (Fig. 7) used to ascertain thetemperature at the bottom or at any intermediatedepth are self-adjusting maximum and minimuminstruments, known as Miller-Casella thermometers,from the names of their inventor and maker, and Fig. Outer Casing. are so constructed as to resist the pressure of thewater at very considerable depths. They consist ofa curved tube with a bulb at each end, one ofwhich is filled with creosote, the expansion andcontraction of which gives the temperature. The APPARATUS AND APPLIANCES USED. 51 creosote acts on a small quantity of mercury in thetube, which rises or falls as the creosote expands orcontracts. In each of the tubes above the mercury is a smallmetallic index, having a hair attached to it, which,pressing against the glass tube, acts as a spring, andkeeps the index in its place, so as to be read off andrecorded. It is evident that the bulb of the thermometerwould be exposed to the pressure of the water aswell as the temperature ; to prevent this, an additionalbulb is blown outside the bulb of the thermometer;this is partially filled with spirit, which is boiledbefore it is hermetically closed, so that
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Keywords: ., bookcentury180, bookdecade1870, booksubjectvoyagesaroundtheworld
