The Rev. Dr. Callan on a new form of Galvanic Battery. 49 



say, nearly a sixth, was necessary for this. J see in this a new 

 analogy between magnetism and diamagnetism. They both 

 diminish if the temperature augments, &c. It appears, more- 

 over, that the diamagnetism of bismuth has its limit (its mini- 

 mum) like the magnetism of iron and of nickel, &c. 



i shall take the liberty to send you my new memoir, which 

 is now in the hands of M. Poggendorff, as soon as it shall 

 appear. Perhaps 1 shall have the pleasure of bringing it 

 myself to London. Accept, Sir, the assurance of my deep 

 respect. 



Bonn, June 5, 1848. 



Plucker. 



IX. On the Construction and Power of a new form of Galvanic 

 Battery. By the Rev. Nicholas Callan, D.D., Professor 

 of Natural Philosophy in Maynooth College*. 



IN a paper published in the August Number of the London 

 Philosophical Magazine, I described several experiments, 

 which clearly prove that, as a negative element of the nitric 

 acid battery, lead coated with chloride of gold or platina, or 

 with borax dissolved in dilute acid, is superior to platina, and 

 that cast iron is fully as powerful as platina. I have since 

 compared, in various ways, the power of a cast-iron battery 

 with that of a Grove's of equal size. The cast iron was ex- 

 cited by a mixture consisting of about four parts of sulphuric 

 acid, two of nitric acid, and two of nitre dissolved in water. 

 The platina was excited by equal parts of concentrated nitric 

 and sulphuric acid. The zinc plates of both batteries were 

 excited by dilute sulphuric acid of the same strength. The 

 cast-iron battery was considerably superior to Grove's, in its 

 magnetic power, in its heating power, and in its power of 

 producing decomposition. The magnetic effects of the two 

 batteries were compared by means of a galvanometer and of 

 a small magnetic machine. Grove's produced a deflection of 

 82°; the cast iron caused a deflection of 85°. When the vol- 

 taic currents of the two batteries were sent simultaneously in 

 opposite directions through the helix of the galvanometer, the 

 current from the cast-iron battery destroyed the deflection 

 caused by Grove's, and produced an opposite deflection of 60°. 

 In the magnetic machine the cast-iron battery produced fifty 

 revolutions in a minute ; Grove's produced only thirty-five in 

 the same time. 



The superiority of the heating power of the cast-iron bat- 

 tery was shown by its fusing a steel wire, which Grove's only 



* Communicated by the Author. 

 Phil. Mag. S. 3. Vol. 33. No. 219. July 1848. E 



