Cresson.] OU^t fJ^unelS, 



chain of considerable strengtii, althougli its component parts are not 

 mechanically connected together. The closer the contact of the ends of 

 the bars the stronger will be the chain. 



If with isolated bars we can obtain a connecting force equal to many- 

 pounds by close contact, how much stronger must be the connecting force 

 when exerted between molecule and molecule. 



Such an argument undoubtedly leads to the conclusion that bars satu- 

 rated with magnetic force should certainly be stronger than those that 

 are not. 



Faraday announced that "there existed lines of force within the mag- 

 net of the same nature as those without. What is more they are exactly 

 equal in amount with those withoiit. They have a relation in direction 

 to those without ; in fact are continuations of them, absolutely unchanged 

 in their nature." 



To determine the effect of magnetic force upon the tensile strength of 

 Iron and Steel,* bars of each were selected and cut into suitable lengths 

 for use in the breaking machine and numbered. 



Nos. 1, 3, 5, &c., were broken in the usual manner. 



Nos. 2, 4, 6, &c., whilst in the breaking machine were suri'ounded by 

 a suitable coil of copper-wire, through which a current of galvanic elec- 

 tricity was passed during the operation of breaking. 



The results obtained from the magnetic Steel bars were about one per 

 cent, less than those obtained from the non-magnetic, and from the mag- 

 netic soft Iron bars about three per cent, less than fi-om the non-magnetic. 



Both the Steel and Iron bars became heated whilst within the influence 

 of the current of electricity, the soft Iron more so than the Steel. 



It occurred to me that the depreciation of strength might have been 

 caused by the rise of temperaturef in the bars, and I accordingly prepared 

 permanent magnets from alternate sections of a steel bar and repeated 

 the experiments comparing the cold magnets with the unmagnetized sec- 

 tions of the same bar. The results showed no appreciable difierence in 

 strength between the magnetic and non-magnetic sections. 



To test the matter still further, bars of Steel were so magnetized as to 

 present a j)ole at one end, the other in the middle of the bar, with one 

 end neutral, that is, one end of the bar attracted the North or South pole 

 of a magnetic needle and repelled the South or North, and the other end 

 of the bar attracted either pole of a magnetic needle. 



* The Steel employed in the experiment was " Jessop's Round Machinery," }^ inch 

 rod — 



and hvol^p nt \ maximum, 127,934 lbs. 

 ana DioKe at ^ n-,iniQ,um, 125,C94 lbs. 



per square inch of section. 



The Iron broke nt $ maximum, 59,948 lbs. 

 1 ne iron DroKe at ^ miajj^uDj^ 56^887 lbs. 



per square inch of section, 

 t For effects of temperature upon the tensile strength of Iron, see Report of the Com- 

 mittee of the Franklin Institute of Pennsylvania, — "upon the strength of materials 

 employed in the construction of Steam Boilers." Experiments made at the request 

 of the Treasury Department of the United States (Jan'y 4th, 1831— Jan'y 5th, 1837). 



