ELECTRICAL APPARATUS. 



297 



Apparatus to Fire *'& 3ir - 



Spirits of Wine, or 

 ther. '(Fig. 347.) 

 This consists of a 

 rod, having a knob 

 at each end, support- 

 ed horizontally on 

 an insulated stand. 

 Through one of the 

 balls slides a wire, 

 vertically,with a knob 

 at one end, beneath 

 which is placed a me- 

 tallic cup for the spi- 

 rits. To use, place it 

 so that the ball, a, can receive sparks from the prime con- 

 ductor. Pour spirits of wine into the cup, e, till the bottom 

 is just covered. Place the cup under the wire, d, then turn 

 the machine, and the sparks that are received by a will fly 

 from the wire through the cup, and inflame the spirits. 

 Warming the spirits will cause it to take fire more readily. 



Price, $2.25. 



Stand for the Fusion of Wire by F] s- 313. 



the Electric Spark. (Fig. 348.) 

 The fusion of wire is sometimes 

 employed as the test of electrical 

 power, in which case it should be 

 taken that the length of the circuit 

 is always the same, and that the 

 degrees of ignition are uniform ; 

 for a wire may be melted with but 

 slight variations of appearance, 

 when very different quantities of 

 electricity have been transmitted 

 through it. The lowest degree of 

 perfect ignition ought therefore to be obtained in all compa" 

 rative experiments, and its phenomena should be uniform 

 that is, as soon as the discharge is made, the wire should 

 become red hot in its whole length, and then fall into drops. 

 In order to ensure a perfect uniformity in this respect 

 throughout a series of experiments, Professor Hare has in- 

 vented the apparatus shown in the cut. This consists of 



