54 EFFECT or MAGNETISM OTJ TUBES. 



On the different Forces tcith which Tubes, Bars, and GyJin^ 

 ders, adhere to a Magnet, In a Letter from Mr, E. 

 Lydiatt. 



To Mr. NICHOLSON. 

 SIR, 



Jl HROUGH the medium of your scientific Journal I 

 am anxious to obtain information on some magnetic pheno- 

 mena, which 1 have lately noticed to ]\ave taken pU\ce on 

 applying? difierenl shaped conductors to connect the poles 

 of a horseshoe mat^net. 



In preparing the introductory course of lectures on the 



Ar iron tube philosophy of the mechanic arts, which I have delivered this 



connecting the ic--/«i-- tii 



poles of a season at the ocientinc Institution, 1 had occasion to make a 



horseshoe f^^y experiments on the magnetic property of iron and steel ; 

 hered with ^" ^^^ course of which I happened to place a piece of iron 

 freatforce. tube in contact with the two poles of a horseshoe magnet 

 composed of thin bars; and found to my surprise, when I 

 attempted to remove it, that a considerably greater force 

 was required, than that necessary to seuaiate the conductor 

 which belongs to the magnet, which, as usual, was a square 

 piece of iron with a ring attached, ai.d presenting a flat sur- 

 face equal to the combined polar surfaces of the three bars 

 cortiposing the magnet. This striking singularity induced 

 me to ascertain the relative force required, to overcome the 

 different degree of attraction. 



I firsf applied the conductor belonging to the magnet. 

 Its adhesion to and, by suspending weights from the ring, found, that it 

 23l^ll^''''" kparated with 5lb. I then supplied its place with the tube, 

 which was a piece of gun-barrel about two inches in length, 

 attached longitudinally from one pole to the other ; and by 

 passing a wire through it, and twisting the two extremities 

 into a hook, I suspended the weights, and found that 1 li|b 

 were requisite to separate it from the magnet. From this 

 experiment it will be evident, that the relative degree of 

 attractive force, exerted by the magnet on these two differ- 

 ent conductors, is as 10 to 23. 1 repeated the experiment 

 get eral times, awl the results were invariably the 9ame. 



The 



