380 Foreign and Miscellaneous Intelligence. 



kind. Powerful attraction is first felt ; this on a sudden fails, and the 

 hand with the iron gives way, but the force is so instantly renewed, that 

 the hand is violently drawn up again by an attraction as great as ever. 



The moment the electric communication is completed, the iron is 

 magnetised to a maximum, and bears its greatest charge. On in- 

 creasing the voltaic apparatus in force, by adding to it another, ex- 

 posing 6 square feet of zinc, so as to make 17 square feet of surface 

 altogether, no increase of magnetic power was conferred upon the 

 arrangement ; nor by using a higher charge was any increase of 

 power obtained, the maximum effect of the iron had been developed 

 in the first instance. Whether the spiral were of copper or brass 

 wire, made no difference. When it was iron wire, -f^ of an inch in 

 diameter, and prevented from touching the curved soft iron by inter- 

 vening silk, the weight taken up was rather higher, being 861b. 



A larger soft-iron horseshoe magnet was now made ; the iron 

 was 2J inches in diameter; the chord of its arc was 12J inches; the 

 spiral was brass wire ^ of an inch in diameter, and made 44 turns. 

 The magnet weighed 261bs. and its connecting piece 41bs. With 

 the voltaic apparatus of ] 1 square feet, this arrangement supported 

 1391bs. ; this was raised to 1541bs. by using an iron spiral, with silk 

 between it and the magnet. This is the maximum to which M. Moll 

 has carried "his experiments; but the force exerted is enormous, and 

 at the same time instantaneous ; and it is extraordinary to see an 

 arrangement, which at one moment can support this weight, lose all 

 its force merely by breaking or altering a distant contact and again 

 have it as fully renewed. 



On trying to heighten the power of an ordinary steel magnet, 

 now capable of supporting 51bs., but formerly much more, these means 

 failed entirely : though left surrounded by the spiral for a long time, 

 its force remained at 51b. The powerful electro -magnets of soft iron 

 just described have, however, every power of ordinary magnets in 

 touching or affecting steel bars, or in strengthening and reversing the 

 poles of ordinary magnets. 



There is a magnet in the Teylerian Museum at Harlem, which sup- 

 ports 2301bs. ; there are, perhaps, one or two other very powerful 

 ones, but except these, the electro-magnet of Professor Moll is the 

 most powerful of any known magnets, and yet is, probably, far short 

 of what might be effected by similar means*. 



6. LAWS OF ELECTRICAL ACCUMULATION." 



Mr. Han-is, of Plymouth, has made an extensive series of experi- 

 ments on the laws of the accumulation of ordinary electricity. The 

 details of these experiments, with illustrative plates, are published in 

 the Transactions of the Plymouth Institution, 1830. We have not 

 space for more than the conclusions at which he arrives. 



i. An electrical accumulation may be supposed to proceed by 



k * Bib, Univ., 1830, p. 19. 



