The boys generally came to me in pairs, and each pair having worked up some illustration of heat produced by electricity reported it to the club. These were spread by the secretary in due form upon the minutes of the club and constituted "The Proceedings of the Science Club." [Illustration: Fig. 69] 1. _The Electric Sad Iron_ (Fig. 69).--Removing three screws the iron comes apart, revealing a lot of No. 24 German silver wire wound upon a sheet of mica. This is put between other sheets of mica (Fig. 70) and tucked away within the body of the iron. German silver offers about twice the resistance of iron when it is cold, but, at the temperature of the sad iron when in use, there is not much difference between the resistance of the two metals. German silver wire, however, does not rust as iron wire would, and hence it is chosen. German silver is an alloy of copper, zinc, and nickel. [Illustration: Fig. 70] We put the 112-volt current upon this wire of the iron, and according to the ammeter it passed 4 amperes. Its resistance must therefore have been 28 ohms. (112 volts)/(28 ohms) = 4 amperes Electricity costs us about 10 cents per kilowatt hour. That is 10 cents for 1000 watts for an hour, or 1 cent for a hundred watts for an hour, or, on a 100-volt current, 1 cent for an ampere for an hour. It, therefore, costs about 4 cents or, more accurately, 4-1/2 cents an hour to heat this iron. Persons sometimes carry electric irons with them, when they travel, to iron pocket handkerchiefs and other small articles while stopping at a hotel. Before connecting an iron in a chandelier one must know the voltage used in the building. If the voltage in use in the building is not the same as that stamped upon the iron, it is not safe to connect it. Not knowing this, many persons have had the embarrassment of "blowing a fuse" and extinguishing their own lights, and perhaps those of others in the same building, and very likely also ruining the iron.