Van Nostrand's eclectic engineering magazine . branches, and a pointon one wire may be connected to a point onthe other by a cross-wire, where the tensionof the current is the same, without at allaffecting the flow of current on the twolines. For, as the flow of current is causedby a difference of tension between thebattery and the point with which it is con-nected by the line-wire, and as the tensionof the currents at the two points on thewires connected by the cross-wire is thesame, no current will flow through thecross-wire. And a galvanometer inserted inthis cross-wire will, of course, sho
Van Nostrand's eclectic engineering magazine . branches, and a pointon one wire may be connected to a point onthe other by a cross-wire, where the tensionof the current is the same, without at allaffecting the flow of current on the twolines. For, as the flow of current is causedby a difference of tension between thebattery and the point with which it is con-nected by the line-wire, and as the tensionof the currents at the two points on thewires connected by the cross-wire is thesame, no current will flow through thecross-wire. And a galvanometer inserted inthis cross-wire will, of course, show nodeflection. In Fig. 3, suppose the current to startfrom E and flow to post 1. Here it divides,one-half passing by wire* A, 3, B, to 2, andthe rest by 0, 4, D, to 2, and thence the APPLIED ELECTRICITY. 59 current returns to battery. The resistanceof the sides A and C, and B and D, beingalike, the tension of the two portions of thecurrent, at 3 and 4, is the same, and nocurrent will pass across, from 3 to 4, throughthe galvanometer. Fig. 2. sistance which we will insert between thebinding posts at D. Say we put 20 ohmsin at C, and 1 at A. The needle is deflect-ed strongly. Now insert resistance at B untilthe needle comes back to zero. Say itrequires 250 units. Then, which is the resistance at D. If the resistance to be measured issmall, you may insert equal amounts at Aand C, and then the number of units in-serted at B will exactly equal D. There are two forms of galvanometersin this country, made on the above prin-ciple : Siemens and Gray & Bartons. Thelatter we will describe first, as its arrange-ment is similar to the diagram, Fig. 3. ELEVATION OF GAUGAIN GALVANOMETEK. * Again : suppose we insert at A a re-sistance of 10, at B 100, at C 500, and atD 5,000. We shall find that the needle onthe cross-wire still refuses to deflect. Be-cause the current divides at 1, inversely asthe resistance of the two routes 1, A, 3, and1, C, 4; and the resistance at C being 50times as great
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