308 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



uninterrupted line ; and when put crosswise, there shall be 

 a want of contiguity at that place, as shown at D. 



Pass a shock from A to E, while the ball remains on and 

 the wire is continuous, and it will make a loud report with- 

 out disturbing either piece of wood. 



Pass a shock, or rather endeavor to do so, with the upper 

 ball taken off, so that the point is displayed. The fluid will 

 pass and discharge the jar, but not in the manner of the 

 shock, and no report will be heard. 



Now place either of the pieces of wood crosswise, and 

 restore the ball to the top. The shock will pass and throw 

 out the piece of wood that was placed crosswise, but not 

 disturb the other piece. 



Let the piece of wood be placed crosswise, as in the last 

 experiment, but remove the ball. Upon discharging the 

 Leyden jar, a real shock will pass, and the wood will be 

 displaced, although a point terminates the apparatus. 



Price, $1.75 and $2.50. 



Fig.358. Electrical Pyramid. (Fig. 368.) This is 



an apparatus of the same nature as the last, 

 and is to be used in the same manner. A is a 

 four-sided pyramidal piece of wood, or more 

 usually consists of four pieces fitting on to 

 each other. A line runs down the whole in 

 front, and is, moreover, continued down the 

 base, B ; continuity being occasioned by a 

 small square, as in the thunder house. This 

 is marked D in the cut, and is seen with its 

 wire placed sideways. Upon this movable 

 square, and upon the back of the base, the 

 upper portion is supported by three balls. 

 When a shock is sent from E to F, the square 

 D is thrown out, and the upper part of the 

 pyramid falls. Price, $2.00 and $3.00. 



Lightning Conductors. The identity of the electric fluid 

 with lightning was one of the first established facts rela- 

 tive to atmospheric electricity, and as it was the first in 

 time, so it is also in importance to us, teaching not merely 

 the origin and properties of that mighty power of nature, 

 but also how to escape from its direful effects. The very 

 appearance of lightning would induce us to attribute it to 



