'i-IS The Rev. N. J. Callan on a 7ieti} Galvanic Battery. 



iron bar, and with the number of plates when they are large ; 

 but with small plates the increase is very gradual when their 

 number exceeds a hundred. With twenty of our large plates, 

 an iron bar, nearly 3| U)s. weight, was attracted to a horse-shoe 

 eJeciro-magiiet through the distance of an inch, and with ten 

 plates the same bar was attracted to the same magnet, only 

 through the distance of about half an inch. Again, with the 

 twenty plates, the attraction of the same magnet for a sewing- 

 needle was sensible at the distance of 15 inches, and with ten 

 plates the attraction was sensible at the distance of 10 inches. 

 Thirdly, that the shock from tlie electro-magnet increases 

 within certain limits with the length and thinness of the iron 

 bar, and nearly in proportion to the number of plates when 

 they are large. 



When the voltaic current was sent from a battery of 280 

 four-inch plates, through the heHacal wire coiled round a steel 

 bar about 20 inches long and an inch thick, the steel became 

 almost as strongly magnetic as if it were iron ; and when the 

 connexion with the battery was broken, the steel did not relaiii 

 more than about j--^ of its magnetism. 



In a paper published in the last (August) number of the 

 Philosophical Magazine, Dr. Ritchie says that the use of 

 the electro-magnet in the apparatus for continued rotation was 

 long since abandoned, because it was incapable of inducing 

 magnetism in an iron bar at a distance. Now he will find 

 that, if instead ol" a single copper and zinc plate, a battery of 

 20pairsoi largeplates, or of 200 small ones be used, the electro- 

 magnet will have a greater power of inducing magnetism at 

 a distance than any permanent magnet. 



The advantages of the battery I have described are, first, 

 that it supplies the place of all the various kinds of voltaic 

 batteries, of the battery for producing a Itfrge quantity of 

 electricity of low intensity, of the battery for exciting a large 

 quantity of electricity of the intensity necessary for the rapid 

 fusion and deflagration of metallic wires, and of the battery for 

 producing an electric current of high intensity; and secondly, 

 that it enables a person to compare the power of the very 

 same zinc and copper plates acting as a single pair, with their 

 power when they act as 2, 3, 4, 5, 6, 10, or 20 voltaic circles. 



Nicholas Callan. 



Maynooth College, August 23, 1836. 



