[LB039051], Letter from Thomas Alva Edison to Edison Machine Works, Samuel Insull, March 24th, 1890
https://edisondigital.rutgers.edu/document/LB039051
Transcription
March 24, 1890 Samuel Insull, Esq., Gen'l Manager The Edison Machine Works, 44 Wall Street, New York City. Dear Sir:- I have your letter of 22nd instant, extract from a letter received by you from H. Ward Leonard, with relation to carbon brushes, and in reply would say that I am very much opposed to the use of these brushes, except where it is actually necessary Good copper brushes with fair attention are the best that can be devised; but, where no attention can be given and load suddenly varies, or where there are ignorant, careless attendants, then carbon might be used. I have always stated that instead of carbon the German silver connection wire between commutator and armature is the most perfect devices known to stop sparking when load varies. Yours very truly, Thos A. Edison