in Electricity and Magnetism. 379 



preceding formula; their power diminished as they ap- 

 proached, in the ratio here shown : — 



Distance of magnets apart. Magnetic power. 



But the loss was only temporary, as they recovered their 

 former power immediately that they were separated. [Their 

 distances apart are reckoned from the middle of the thickness 

 of each; so that when they are said to be at a distance 0*05, 

 they are in actual contact.] 



A number of hardened steel sheet magnets, 8 inches long, 

 0*8 wide, and about 0*03 thick, were placed in a light frame- 

 work of wood, one over another at equal distances, as in the 

 preceding experiment, and the whole mass slung by a thread 

 of parallel silk fibres, and the magnetic power ascertained by 

 vibrations ; this pile of magnets was kept one foot high by 

 using fewer magnets when they were placed further apart*. 

 The power of each individual magnet was diminished as they 

 approached, in the ratio here shown : — 



Distance of magnets apart. Magnetic power, 



inch. fn. 



* Only forty.eight magnets were used ; therefore, when they were placed 

 very close, the pile could not be made one foot high : but the effect of 

 increasing the height of the pile, the distance between the magnets re- 

 maining the same, was ascertained ; and so the effect of a pile one foot 

 high was calculated from experiments with one of a less height. 



f The results given in the second column, are always comparative with 

 the aggregate power of the same magnets when placed far apart. 



