328 THE DEBT OF THE WORLD TO PURE SCIENCE. 



completed tbe series of fundameutal discoveries, and since that time 

 everything has been elaboration. 



Oersted's discovery respecting the influence of an electric current, 

 closely followed by that of Arago in the same direction, opened the way 

 for Faraday's complete discovery of induction, which underlies the con- 

 struction of the dynamo. This ascertained, the province of the inven- 

 tor was well defined — to conjure some mechanical appliance whereby 

 the principle might be utilized. But here as elsewhere the work 

 of discovery and that of invention went on almost pari passu; the 

 results of each increased those of the other. The distance from the 

 Clark and Page machines of the middle thirties, with their cumbrous 

 horseshoe magnets and disproportionate expenditure of i^ower, to the 

 Siemens machine of the fifties was long, but it was no leap. In like 

 manner slow steps marked progress thence to the Gramme machine, in 

 which one finds the outgrowth of many years of labor by many men, 

 both investigators and inventors. In 1870, forty years after Faraday's 

 announcement of the basal principle, the stage was reached whence 

 progress could be rapid. Since that time the dynamo has been brought 

 into such stage of efficiency that the electro-motor seems likely to dis- 

 place not merely the steam engine, but also other agencies in direct 

 application offeree. The hor^e is passing away and the trolley road 

 runs along the country highway; the longer railways are considering 

 the wisdom of changing their power ; cities are lighted brilliantly where 

 formerly the gloom invited highwaymen to ply their trade, and even the 

 kitchen is invaded by new methods of heating. 



Long ago it was known that if the refining of pig iron be stopped 

 just before the tendency to solidify became pronounced the wrought 

 iron is more durable than that obtained in the completed process. 

 Thus, imperfectly refined metal was made frequently, though uninten- 

 tionally and ignorantly. A short railroad in southwestern Pennsylva- 

 nia was laid in the middle sixties with iron rails of light weight. A 

 rail's life in those days rarely exceeded five years, yet some of those 

 light rails were in excellent condition almost fifteen years afterwards, 

 though they had carried a heavy coke traffic for several years. But 

 this process was uncertain, and the best puddlers could never tell 

 when to stop the process in order to obtain the desired grade. 



When a modification of this refining process was attempted on a 

 grand scale almost contemporaneously by Martien in this country and 

 Bessemer in England, the same uncertainty of product was encountered; 

 sometimes the process was checked too soon, at others pushed too far. 

 Here the inventor came to a halt. He could use only what was known 

 and endeavor to improve methods of application. Under such condi- 

 tions the Bessemer process was apparently a hopeless failure. Another, 

 however, utilized the hitherto ignored work of the closet investigator. 

 The influence of manganese in counteracting the effects of certain inju- 

 rious substances and its relation to carbon when present in pig iron 



