CHAPTER III. 



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 i 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. — Constructs a Standard Galvanometer. — 

 Repeats His Experiments. — Discovers Fundamental Law 

 of Electro-Magnetic Attraction. — Cojitemplates Perpetual 

 Motion. — Explains Law of Electro-Magnetic A ttraction. — 

 Measures Current, Velocity ; Resistance ', and Estimates 

 Zinc Consumed in Producing the Current. — Obtains 

 1 Duty ' per lb. of Zinc. — Realizes Resistance to tlie 

 Current Induced by the Motion of the Magnet. — Refers 

 to Faraday, Ohm, &c. — Determines Lazv of Induced 

 Resistance. — Discovers Equivalence of Mechanical Effect 

 to the Electric- Action, and CJiemical- Action Expended in 

 its Production. — Introduces Absolute Electric Measure- 

 ment. — Concludes that the Electro- Magnetic Engine can 

 never Compete with the Steam Engine. — Sees a great 

 Philosophical Discovery before him. 



It was with the simple object of improving Sturgeon's 

 electro-magnetic engine that Joule, in 1838, then 19 years 

 of age, entered upon the first stage of his great research, 

 publishing the results in letters to Sturgeon's " Annals of 

 Electricity." He was impressed, like many older men, with 

 D 



