|leseai‘r|cs 011 .^miaiiro-^lcttrk #titerafors. 
By Peofessor SILVANUS P. THOAIPSON. 
[Abstract.] 
FTEB giving a brief sketch of the earlier machines, illus- 
jLI. trated by the oxy -hydrogen lantern, the lecturer pointed 
out that one of the most important requirements for a good 
dynamo was that it should give a current of uniform electro- 
motive force, or “ electric pressure,” no matter how great or how 
small the resistance in circuit, d hus, if to begin with ten 
lamps are working, and then nine are tuiTied off, the remaining 
one should give the same light as before. Till recently, no 
attempts had been made to obtain a scientific basis for the 
impi’ovements introduced, but now that state of things was 
being changed. The first step forward was taken when graphic 
representation of the work done by a machine was introduced by 
the construction of diagrams similar to the ordinary indicator 
diagrams of steam engines, with the difference that vertical 
distances represent electromotive force, and horizontal distances 
current. If for any current the electromotive force remain 
constant, then the diagram will be a horizontal line. In the 
case of a machine giving such a diagram, the brilliancy of the 
one light mentioned above would be unaltered in spite of 
altering the current to the extent we should do by turning off 
the other nine lamps. This has been practically realized by 
Mordey’s modification of the Schuckert machine. In that case, 
out of 101 incandescent lamps in full operation, 100 were sud- 
