[Electric engineering.] . untedon the slate front. By turning the hand wheel H, any num-ber of sections maybe cut in or all rheostatsare made so thatturning the handleto the right will cutin resistance andlower the voltage ofthe dynamo. Thisis the same direc-tion that an ordi-nary globe valve isturned to shut offthe steam or most modernslate or marbleboards, the rheostat is mounted on the back of the panel,and all that appears on the frontis the hand-wheel necessary foroperating it. Fig. 34 shows a rheostat ar-ranged in this way. The oneshown is of the enamel type,in which
[Electric engineering.] . untedon the slate front. By turning the hand wheel H, any num-ber of sections maybe cut in or all rheostatsare made so thatturning the handleto the right will cutin resistance andlower the voltage ofthe dynamo. Thisis the same direc-tion that an ordi-nary globe valve isturned to shut offthe steam or most modernslate or marbleboards, the rheostat is mounted on the back of the panel,and all that appears on the frontis the hand-wheel necessary foroperating it. Fig. 34 shows a rheostat ar-ranged in this way. The oneshown is of the enamel type,in which the wire is made upinto flat zigzag coils and embed-ded in enamel on the back ofa ribbed iron plate. This holdsthe wire securely in place andat the same time allows it toimpart the heat generated to theribbed iron plate, which radiatesit. The figure shows the oper-ating wheel H that moves the fig. a over the contacts b ; t, f are the terminals of therheostat, and the whole is bolted to the panel by means ofbolts § 17 ELECTRIC LIGHTING. 33 GROUND DETECTORS. 27. It is necessary to have some device by means ofwhich grounds on the system may be detected. A volt-meter makes a very good ground detector, because it not
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