Thomas Alva Edison, Journal Notes, pages 2- 3, 1875

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Thomas Alva Edison, Journal Notes, pages 2 - 3, 1875

perfect and conspicuous copies ever taken on the
Autographic press were taken this evening with ink
formed of printers ink thinned by castor oil and
ground in a mortar some two weeks previously.
October 3, 1875 Thos A Edison.
Chas Batchelor. James Adams

No 2 Electric Pen
In testing a new model pen this evening, one with all
the mechanisms put in an iron frame (cast) we found that
it did not approach in power or speed the rubber frame
pen made by John Ott. The spools of the iron frame
pen were two sizes of wire longer than Otts magnets.
Thinking perhaps that the resistance was too great
or that owing to the greater number of convolutions
the self induction delayed magnetization we unwound
one layer from each spool, but this did not appear
to increase the power or speed materially. We then
tested R on Galvanometer of both pens & found them
about the same. We used the cast iron frame as a
yoke to the engine magnet and found by testing that
there were free poles at the poles where the cores
are connected to the cast iron back. These free poles
became nearly as strong when the armature was in
contact with the regular poles, as the regular poles
we then in addition to the cast iron yoke inserted
a small soft iron yoke about 3 - 64 thick. This made
some difference in the speed still there were free
poles. We then took the magnet out of the
engine frame for testing, found that with the
small soft iron back there was scarcely any free
poles when the front armature was not in contact
with the cores. This armature is 3 - 32 thick, but when
in connection the free poles were very strong
perhaps they would attract with a force almost
equal to the regular ones, by making the
armature thicker the free poles became stronger
If the yoke was increased in thickness the free
poles became weaker and it is very probably that


if both the yokes cores and armatures had the
same mass of metal and all in good contact
no magnetism or free poles could be detected
but the moment the iron circuit, or perhaps
we might call it the magnetic circuit was
weakened by decreasing the mass of the iron
at any one point free poles would appear
at that point, hence to obtain the maximum
power the mass of iron in the yoke should
be so great as to offer but little resistance
to the passage of the magnetism so as not
to cause free poles to go to the point of greatest .R. those
in front of the the armature, and it may be
found that a thin armature will increase
this tendency by increasing the resistance
we also discovered a Phenomenon. thus
with a thick armature and back or yoke
considerably thinner a nail was attracted
only on opening and closing the circuit
further tests should be given this and the
armature& yoke proportions.
Oct 6th 1875. All night
Thos. Edison
Chas. Batchelor
James Adams

Autographic Pen
No 3
Worked on pen all night. (model pen) found that
cams gave vibrating pen too great a movement (ie)
three times more movement that was necessary
to puncture the paper, hence engine had to do more
work, altered it so that it would give much less
movement. There was a great improvement in the
speed of the engine, but not enough to account for
the unsatisfactory working of the pen. We tested


Thomas Alva Edison
Date written
x in x x in
Penmanship Style
Courtesy of Thomas Edison National Historical Park
The Thomas Edison Papers, Rutgers University [1]
Link for electric pen[2]
File name
Edison Thomas Alva 1847-001-001-001

Thomas Edison Electric Pen ac0184-NE1691002.jpg