The construction of Dynamos, Motors, Armatures, Armature Windings, Installing of Dynamos. =ELECTRICAL GUIDE, NO. 3= Electrical Instruments, Testing, Practical Management of Dynamos and Motors. =ELECTRICAL GUIDE, NO. 4= Distribution Systems, Wiring, Wiring Diagrams, Sign Flashers, Storage Batteries. =ELECTRICAL GUIDE, NO. 5= Principles of Alternating Currents and Alternators. =ELECTRICAL GUIDE, NO. 6= Alternating Current Motors, Transformers, Converters, Rectifiers. =ELECTRICAL GUIDE, NO. 7= Alternating Current Systems, Circuit Breakers, Measuring Instruments. =ELECTRICAL GUIDE, NO. 8= Alternating Current Switch Boards, Wiring, Power Stations, Installation and Operation. =ELECTRICAL GUIDE, NO. 9= Telephone, Telegraph, Wireless, Bells, Lighting, Railways. =ELECTRICAL GUIDE, NO. 10= Modern Practical Applications of Electricity and Ready Reference Index of the 10 Numbers. Theo. Audel & Co., Publishers 72 FIFTH AVENUE, NEW YORK FOOTNOTES: [1] NOTE.--In 1749, Benjamin Franklin, observing lightning to possess almost all the properties observable in electric sparks, suggested that the electric action of points, which was discovered by him, might be tried on thunderclouds, and so draw from them a charge of electricity. He proposed, therefore, to fix a pointed iron rod to a high tower, but shortly after succeeded in another way. He sent up a kite during the passing of a storm, and found the wetted string to conduct the electricity to the earth, and to yield abundance of sparks. These he drew from a key tied to the string, a silk ribbon being interposed between his hand and the key for safety. Leyden jars could be charged, and all other electrical effects produced, by the sparks furnished from the clouds. The proof of the identity was complete. The kite experiment was repeated by Romas, who drew from a metallic string sparks 9 feet long. In 1753, Richmann, of St. Petersburg, who was experimenting with a similar apparatus, was struck by a sudden discharge and killed. [2] NOTE.--Suppose that the conditions are as in the fig. 34, that is, the segment A_1 is positive and the segment B_1 negative. Now, as A_1 moves to the left and B_1 to the right, their potentials will rise on account of the work done in separating them against attraction. When A_1 comes opposite the segment B_2 of the B plate, which is now in contact with the brush Y, it will be at a high positive potential, and will therefore cause a displacement of electricity along the conductor between Y and Y_1, bringing a large negative charge on B_2 and sending a positive charge to the segment touching Y_1.