290 



BENJ. PIKES, JR., DESCRIPTIVE CATALOGUE. 



Spiral and Flyer. (Fig. 330, preceding page.) This 

 consists of a glass tube coated as a spiral, and having a cup 

 with a pointed wire projecting, in which is placed a flyer. 



Price, $3.00. 



Fig. 331. 



Fig. 3 .2. 



Revolving Glass G7ofo. (Fig. 331.) 

 This apparatus consists of a glass 

 globe delicately suspended on a point, 

 and having a mahogany base ; on one 

 side and opposite the centre of the 

 globe, there is a brass ball mounted 

 on a glass pillar, having a hook for at- 

 taching a chain ; on the other side 

 there is a brass ball with metallic support, 

 having a point projecting towards the centre 

 of the globe. To use, connect the insulated 

 ball with the conductor of the electrical ma- 

 chine by a chain, and the other ball with the 

 floor, or ground ; give the glass globe a rotary 

 motion with the hand ; the globe, on passing 

 the insulated ball, will on that side be charg- 

 ed, and repelled ; but on coming near the 

 point on the opposite side, will be attracted, 

 and the fluid drawn off, thus keeping up a 

 continued rotary motion. Price, $2.50. 



The Aurora Tube. (Fig. 332.) This inte- 

 resting and beautiful experiment is shown by 

 a glass tube of from twenty to forty inches in 

 length, and from one and a half to two and a 

 half inches in diameter, having brass caps 

 cemented on each end ; the lower end having 

 a stop-cock and a brass ball within the tube, 

 the upper end a pointed wire within the tube 

 and a brass ball on the outer end ; the whole 

 is mounted on a base for a support. To use, 

 the tube is exhausted of air by attaching the 

 stop-cock to an air pump ; present the ball 

 to the prime conductor of an electric machine, 

 when the fluid will pass in a continued and 

 beautiful stream, the appearance presented 

 being exactly that offered by the aurora bore- 



