Tables 284, 285. 



PERMEABILITY OF IRON. 



TABLE 284. —Permeability ol lion Rings and Wire. 



This table gives, for a few specimens of iron, the magnetic induction B, and permeability Mi corresponding to the 

 magneto-motive forces H recorded in the first column. The first specimen is taken from a paper by Rowland,* 

 and refers to a welded and annealed ring of " Burden's Best" wrouglit iron. The ring was 0.77 cms. in mean 

 diameter, and the bar had a cross sectional area of o.yi6 sq. cms. Specimens 2-4 are taken from a paper by 

 Bosanquet.t and also refers to soft iron rings. Tlie mean diameters were 21.5, 22.1, and 2^.725 cms., and the 

 thickness of the bars 2.535, 1.295, ^"d ■7544 tins, respectively. These experiments were intended to illustrate the 

 effect of thickness of bar on the induction. Specimen 5 is from Ewing's book,t and refers to one of his own 

 experiments on a soft iron wire .077 cms. diameter and 30.5 cms. long. 



TABLE 285.— Permeability of Transformer Iron.§ 



This table contains the results of some experiments on transformers of (Jie Westinghouse and Thomson-Houston 

 types. Referring to the headings of the different columns, jl/is the total magneto-motive force applied to the iron ; 

 A/ /I the magneto-motive force per centimetre length of the iron circuit: £ the total induction through the mag- 

 netizing coil ; B / a the induction per square centimetre of the mean section of the iron core ; iM / B the magnetic 

 reluctance of the iron circuit; Bl /Mix the permeability of the iron, a being taken as the mean cross section of the 

 iron circuit as it exists in the transformer, which is thus slightly greater tlian the actual cross section of the iron. 



* " Phil. Mag." 4th series, vol. xlv. p. 151. 



+ Ibid. 5th series, vo). xix. p. 73. 



X " Magnetic Induction in Iron and Other Metals." 



§ T. Gray, from special experiments. 



Smithsonian Tables. 



274 



