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TO THE 
AMERICAN JOURNAL OF SCIENCE AND ARTS, VOL. XXXili, No. 2. 
Davenport ie recent Experiments in Plesr Magai Machine 
- (Copy of a letter from Mr. Davenport. j= es 
TO PROF. SILLIMAN, 
tion,t) I have thought proper to state to you the results, believing 
they would not be uninteresting to you 
I chave constructed a machine, with: two. revolving magnets, t 
: feet in length, made of iron three and a half inches in diameter, an ad 
weighing, after being wound with six coils of No. 10 copper wire, 
one hundred pounds ea each: ‘Three stationary magnets of two feet 
diameter, were placed around the periphery making six poles, and 
weighing one hundred pounds each. 
With this machine I produced one hundred revolutions per min- 
ute, with six.sguatelechobaheerzineexpased to to action, surrounded 
with. thin. sheet-copperos:: saicasme Yai 2Sicus 
I then displaced the stationary magnets, and aubssituted one mag- 
net three inches in diameter, forming a semicircle, with the poles 
directly opposite each other, and we eighing about one hundred pounds. 
With this magnet I produced one hundred and fifty revolutions per 
minute, using the same quantity of zine surface. With one revol- 
per minute, with four square feet of sheet zinc. 1 next constructed 
a hollow magnet of two feet in length and four inches in diameter, 
made of boiler i iron, five-sixteenths of an inch in thickness, with four 
* Received after the Journal was finished. 
+ The machine alluded to in the above letter, as now being constructed for the 
Eleetro-Magnetic Association, by Messrs. Davenport & Cook, is nearly comple- 
ted, and is expected to be of about two tons power. Itis formed by a combination 
of small magnets, weighing about four pounds each, and three and a half inches 
between the poles. These magnets are placed, two hundred thirty four in number, 
on an iron shaft six feet in length, and a corresponding number in a circle as sta- 
tionary magnets. 
