137 
stated in his paper respecting the effect of joining the poles 
with a good conductor), and it is only when the machines 
are employed for the production of electric light, or other 
purpose, where the external resistance is considerable that 
this electro-mechanical function of the current comes into 
useful operation. 
The author, before concluding his description of this 
further development of the principle of electro-magnetic 
accumulation, considers it a duty he owes to himself as well 
as to science, that he should not allow to pass unnoticed the 
views and statements of certain writers respecting the place 
and value of his investigations in the history of natural 
knowledge. The peculiar good fortune which enabled him 
to follow up the discovery of a great principle to such 
brilliant results has contributed, accidentally in some 
instances, to establish the idea, that these results are an 
expansion of Faraday’s discovery of magneto-electricity 
rather than a distinct step in electricial science. A brief 
glance at the history and progress of electricity and magnet- 
ism will suffice to show the erroneousness of this view, and 
also that his discovery bears only the same kind of relation 
to that of Faraday as that philosopher’s discovery does to 
those of Galvani, Volta, and Grove in galvanic electricity; 
and of Oersted, Ampere, Arago, and Sturgeon in electro- 
magnetism. That the discovery of the indefinite increase of 
the magnetic and electric forces from quantities indefinitely 
small is a fundamental advance in electrical knowledge, and 
not simply an expansion of known prin ciples or an improvement 
in a machine, as it has been made to appear by some, is evident 
from the fact that the principle since its enunciation in 1866, 
togethei with the author s invention of minor and major mag- 
neto-electric circuits, has been embodied in the machines of 
different forms constructed by Ladd, Holmes, d’lvernois, 
Gramme, and others. Moreover, Faraday himself, while on 
the threshold of his discovery, distinctly negatived its possi- 
