Chemistry and Physics. 403 
Matic rod of thin sheet iron at the ends of ch were fixed 
lead balls, each weighing 300 grams. ‘The steel knife edge, 
Which r agat s in the middle of the rod 
masses, 
Hecessary—the distance of the extra weights, and of the center of 
the pendulum bobs from the knife edge. Dr. Wildi 
x. Repsold of Hamburg, will give excellent results.—PAil. Mag., 
22 J 
Thomson’s water dropper, that this apparatus does not take the 
potential of the air quickly. With a discharge of 8 liters of 
Water in twelve hours, six minutes were necessary in order to 
obtain 7s of the variation of potential; and with a discharge of 
12 liters, five minutes were needed to reduce the apparatus to the 
o 
Sas burner inside a hollow metallic vessel, closed at the top and 
Provided with holes necessary for draft; the metallic burner and 
the outside vessel were connected with a wire. This apparatus 
Serves as a battery, there being an electromotive force developed, 
Which depends: i. Upon the nature of the which is burned; 
2. Upon the nature of the metal of the burner, and 3. Upon the 
