. The London, Edinburgh and Dublin philosophical magazine and journal of science. one from each tube is soldered to one thick copper wire,and the other to another thick wire. These last wires are con-nected with the poles of a battery of one or two large Grovescells. The current then divides itself, and a portion flows througheach wire proportional to the con ducting-power of that current heating the wire causes the air in the bulb to ex-pand and depress the liquid in the tube attached by an amountnearly proportional to the con ducting-power of the wire. If thetubes were filled at fi
. The London, Edinburgh and Dublin philosophical magazine and journal of science. one from each tube is soldered to one thick copper wire,and the other to another thick wire. These last wires are con-nected with the poles of a battery of one or two large Grovescells. The current then divides itself, and a portion flows througheach wire proportional to the con ducting-power of that current heating the wire causes the air in the bulb to ex-pand and depress the liquid in the tube attached by an amountnearly proportional to the con ducting-power of the wire. If thetubes were filled at first to the top, the liquid will, when thecurrent is flowing, fall through different amounts. Fig. 1 showsthe curve when the wires are gold, silver, and various alloys ofgold and silver. If the connexions are changed so that thesame current flows in succession through every wire, the liquidwill be depressed by an amount nearly proportional to the resist-ance of each wire. In fig. 2 we have a similar set of bulbs, into each of which Fig. 2.(Scale one-tenth of the natural size.). passes, through a cork, a bar of metal of the same material as thewire in the corresponding bulb, fig. 1. The metal bars are at their other end secured in a box ofboiling water. The heat conducted by the bars from the box ofwater to the bulb depresses the liquid in the tubes, and a curveis formed by the tops of the columns of liquid of nearly thesame shape as was formed by the heated wires. It is well to protect the bulbs in both cases by enclosing themin little compartments formed of blackened tin-plate. Thesemay be conveniently formed by soldering pieces to form the ver- Royal Society. 301 tical walls of each compartment to a plate at the back. Thisplate has holes bored in it, through which the bars pass. Aplate of metal at the top and bottom close in the bulbs com-pletely ; and the plates are secured in their places by four wiresbent twice at right angles and serving as clamps, as indicated inthe figur
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
