No. 49. Two sheets of aluminum-leaf for the leaf electroscope ([Fig. 57]) and other experiments.
No. 50. One bent wire (H P, [Fig. 57]) used in connection with the leaf electroscope.
No. 51. A dry cell, ordinary size about 7 in. high and 2½ in. in diameter.
No. 52. Enough mercury to amalgamate battery zincs. A wooden pill box containing about half a thimbleful will do.
No. 53. A coil containing 25 feet of No. 24 insulated copper wire for connections.
No. 54. One dozen spring connectors ([Fig. 61]) for making connections. These are made of brass, nickel plated, and do not affect the compass-needle.
No. 55. A telegraph key ([Fig. 68]) without switch. The metal straps are made of aluminum; they are ½ in. wide, and are fastened to a neat wooden base.
No. 56. Three metal plates, each about 2 in. by ¾ in., on which spring connectors (No. 54) are to be pushed in order to join two wires.
No. 57. A current reverser ([Fig. 69]). The straps are made of aluminum and are fastened to a neat wooden base.