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



about the size of a quill, for the purpose of attaching wires 

 and other kind of apparatus. This machine is the best for 

 showing the effect of positive and negative electricity. The 

 conductor to which the rubber is attached is the negative, 

 and the one having the points the positive or prime conductor. 

 If it be required to accumulate positive electricity, a chain 

 must be carried from the negative conductor to the floor. 

 If, on the other hand, negative electricity be required, then 

 the positive conductor must be put in connexion with the 

 ground, and the other insulated. 



Price, with two conductors, 8 inch, $22.00. 



" " " 9 inch, $25.00. 



" " " " 10 inch, $28.00. 



To use the Electrical Machine. Let the machine be care- 

 fully wiped with a clean silk or linen cloth, to free it entirely 

 from dust ; spread a little amalgam evenly along the cushion, 

 turn the machine with rapidity for some time, observing if 

 the whole surface of the cushion is covered with the amal- 

 gam ; remove all the amalgam adhering to the glass, attach 

 a chain to the rubber to connect with the floor, or place the 

 hand on the rubber, gently pressing it, frequently wiping the 

 whole machine with a silk cloth free from dust, which in an 

 excited state it readily attracts. 



The most powerful excitation of the machine is produced 

 as follows. Let the machine be placed within the influence 

 of a good fire, but not so near as to injure any of its parts 

 by the action of the heat. With a flat round-pointed knife 

 spread a little amalgam evenly along the cushion, and return 

 it to its place ; turn the cylinder a few times round ; then 

 take off the cushion, and observe carefully those parts on its 

 surface that have not been touched by the cylinder while 

 revolving ; on these parts put a little more amalgam, and 

 repeat the process of turning the cylinder, and supplying 

 ihe defective parts with amalgam, till every point of that 

 part of the surface of the cushion which presses on the 

 cylinder appears to be properly supplied with amalgam. 

 Take now a piece of leather, about five or six inches square, 

 and spread over one side of it a quantity of amalgam; 

 Inrow back the silk flap, and, turning the machine gently 

 round, applied the amalgamed side of the leather to the 

 cylinder, for the space of two minutes or more, as circum- 

 stances may require, during which time the excitation will be 



