140 Mr. H. A. Rowland on Magnetic Permeability, 



on during the Glacial era, when the continental elevations appear 

 to have reached their highest limit. 



We gather from these facts how it is that a general submer- 

 gence, or an emergence, might characterize cotemporaneously 

 large areas of North America and Europe — as, for example, in 

 the Subcarboniferous, Carboniferous, and Permian periods, du- 

 ring which the rocks show that there was a general parallelism 

 in the movements. If a geanticlinal were in progress over the 

 middle of the Atlantic crust as a result of the lateral thrust in 

 the continental and oceanic crusts there might also be a reverse 

 movement or general sinking along the continental borders, as 

 well as a rise of water about the continents from the diminution 

 in the ocean's depth ; and when the oceanic geanticlinal flat- 

 tened out again through subsidence, the subsiding crust would 

 naturally produce a reverse movement along one or both con- 

 tinental borders. 



From the various considerations here presented, derived from 

 both the continental and oceanic areas, it is apparent that the 

 earth has exhibited its oneness of individuality in nothing more 

 fundamentally and completely than in the heavings of its con- 

 tracting crust. 



The subjects of metamorphism, the earth's interior, igneous 

 eruptions and volcanoes remain for discussion. In addition I 

 propose to consider the steps in the origination of the conti- 

 nental plateaux and oceanic basins, and also to present some facts 

 bearing on the general nature of the infra- Archaean crust — that 

 is, the part below the earth's superficial coatings. 

 [To he continued.] 



XIV. On Magnetic Permeability*, and the Maximum of Mag- 

 netism of Iron, Steel, and Nickel. By Henry A. Rowland, 

 Instructor in Physics in the Rensselaer Polytechnic Institute, 

 Troy,N.Y.f 



[With Two Plates.] 



MORE than three years ago I commenced the series of ex- 

 periments the results of which I now publish for the 

 first time. Many of the facts which I now give were obtained 

 then ; but, for satisfactory reasons, they were not published at 

 that time. The investigations were commenced with a view to 

 determine the distribution of magnetism on iron bars and steel 



* The word "permeability " has been proposed by Thomson, and has 

 the same meaning as " conductivity " as used by Faraday (Tapers on Elec- 

 tricity and Magnetism/ Thomson, p. 484; Maxwell's f Electricity and Mag- 

 netism/ vol. ii. p. 51). 



f Communicated by Professor J, Clerk Maxwell, M,A., F.R.S, 



