? a Pnifina 9 30, 3B 
Are. XIV. <i lectins Maphetie ee constructell by the late 
. W. Campsei, of New Orleans, —communicated by re 
Rippew. 
Tus engine, now in my. pomssseion; was the result of two or 
three years of study and numerous experimental trials. Mr. 
Campbell was a teacher by profession. His opportunities for ac- 
quiring a knowledge of natural science were very limited, but 
his zeal and singleness of purpose are seldom exceeded. He 
died in January, 1838, leaving his design not quite finished. 
His engine differs in some respects from those constructed by 
others. It consists essentially of two large and solid electro- 
magnets, of soft iron, in the form of the letter U, coated with 
coils of copper strips one inch broad by half a line in thickness. 
“These copper coils are insulated by being wound with strips of 
paper. The electro-magnets weigh, each, about one hundred 
pounds, and are arranged horizontally, the opposing poles being 
about eight inches apart. Between them plays the keeper of soft 
iron, K, after — manner. of a piston of a steam engine. ‘When 
the magnet, R, is ¢ ted with an active pair of galvanic plates, 
K is attracted by its poles. A reversed current of the galvanic 
fluid froma smaller pair of plates, is then sent around the mag- 
net, sufficient in quantity to destroy its magnetism the moment 
after the connection with the large galvanic pair is broken. At 
this instant the magnet Lis made to attract the keeper; the con- - 
nection is then broken, and the current reversed as before; and 
thus a-returning horizontal motion is given to the keeper and its 
appurtenances. ‘The connections are broken and reversed by the 
dipping of amalgamated slips of copper into mercury. 
_ New Orleans, November, 1838. 
