IV CONTENTS. 



CHAPTER III. 



PAGE 



Joule's First Research. — Starts to improve Sturgeon's 

 Electro-Magnetic Engine. — Increases the Magnetic Force. — 

 Does not realize His Problem. — Effects the Absolute 

 Measure of ' Work.' — Finds that the Speed is Limited. — 

 Seeks for the Limit in the Magnets. — Fails to find it. — 

 Realizes the importance of Measuring the Current. — Con- 

 structs a Standard Galvanometer. — Repeats his Experi- 

 ments. — Discovers Fundamental Law of Electro-Magnetic 

 Attraction. — Contemplates Perpetual Motion. — Explains 

 Law of Electro-Magnetic Attraction. — Measures Current, 

 Velocity, Resistance, and estimates Zinc Consumed in 

 Producing the Current. — Obtains ' Duty ' per lb. of Zinc. — 

 Realizes Resistance to the Current Induced by the Motion 

 of the Magnet. — Refers to Faraday, Ohm, &c. — Determines 

 Law of Induced Resistance. — Discovers Equivalence of 

 Mechanical Effect to the Electric-Action, and Chemical- 

 Action expended in its Production. — Introduces Absolute 

 Electric Measurement. — Concludes that the Electro- 

 Magnetic Engine can never compete with the Steam 

 Engine. — Sees a great Philosophical Discovery before him. 33 



CHAPTER IV. 



Second Research. — Communicates Results to the Royal 

 Society. — Joule's Motive. — Attributes Proportionality of 

 Chemical and Mechanical Effects to their respective 

 Quantitative Relations to the Electric Action. — Heat in 

 Metallic Conductors. — Proportional to the Square of the 

 Current. — Absolute Measures of Heat, Current, and 

 Electromotive Force. — Heat Equivalent of Electrical 

 Effect. — Heat Developed during Electrolysis. — Electric 

 Origin of Heat. — Heats of Combustion and Electrolysis. — 

 Intensity of Chemical Affinity of Combustibles.— Permanent 

 and Transitory Voltaic Intensity. —Dependence of Affinity 

 on Gaseous or Liquid States.— First Paper before the 



